Lajos Tóth

Neurotoxin induced nerve cell degeneration: Possible involvement of calcium

Neurotoxin induced nerve cell degeneration has been studied in sensory ganglia of newborn and in the area postrema of adult rats following the administration of the selective sensory neurotoxin, capsaicin and the amino acid excitotoxin, glutamic acid, respectively. Light microscopic histochemical, autoradiographic, electroncytochemical and X-ray microanalytical studies revealed that degeneration of certain small-sized, type B primary sensory neurons, induced by capsaicin, was associated with a marked accumulation of calcium predominantly in mitochondria of the damaged ganglion cells. Similarly, monosodium glutamate treatment resulted in the appearance of calcium-containing electron-dense granules in mitochondria of degenerating area postrema neurons. In addition, after a combined administration of 45Ca2+ and capsaicin or monosodium glutamate, significantly higher levels of radioactivity have been detected by liquid scintillation spectroscopy in the Gasserian ganglia and the area postrema, respectively. It is concluded that an enhancement in intracellular calcium level may be intimately involved in the process of neuronal cell death and may represent a common basic mechanism responsible for the development of cellular events leading ultimately to the degeneration of nerve cells.

TRANSPORT OF CHOLINE ACETYLTRANSFERASE AND ACETYLCHOLINESTERASE IN THE RAT SCIATIC NERVE: A BIOCHEMICAL AND ELECTRON HISTOCHEMICAL STUDY

The transport of acetylcholinesterase (AChE) and choline acetyltransferase (ChAc) were investigated by biochemical and histochemical methods. After ligature of one of the sciatic nerves of the rat for varying times—4, 14, 20 and 44 h—the normal levels and the accumulation of AChE and ChAc activities were investigated. It can be inferred from the results that there is a rapid accumulation of AChE activity just proximal to the ligature, while the increase in ChAc activity is less pronounced. Distal to the ligature the level of AChE is above the control value whereas, in contrast to this, the ChAc activity is significantly decreased. Histochemical demonstration of the two enzymes indicates that they are present in the cholinergic axons. The reaction end‐product produced by AChE occurs within vesicles and neurotubules, while the endproduct due to ChAc appears to be free in the axoplasm, bound to neurofilaments and on the outer surface of vesicles and tubules.

Butyrylcholinesterase activity in fenestrated capillaries of the rat area postrema.

In previous papers we have reported on the histochemical localization and possible functional role of acetylcholinesterase in the area postrema of the rat9,1L In the present study the fine structural localization of butyrylcholinesterase activity in the capillaries of the area postrema was analyzed. So far both light and electron microscopic methods, commonly used for the histochemical demonstration of cholinesterases, failed to reveal butyrylcholinesterase activity in these capillaries 2,6,7. Therefore it was a rather unexpected finding that butyrylcholinesterase activity could be demonstrated in the capillaries of this brain region. Investigations were performed on the medulla oblongata of adult albino rats weighing 150-200 g. Under ether anesthesia, animals were perfused through the aorta with a fixative containing 4 ~ formaldehyde (freshly prepared from paraformaldehyde), 2 ~ glutaraldehyde, 0.002 M calcium acetate and 4 ~ sucrose in 0.1 M sodium cacodylate buffer (pH 7.4). After perfusion for 60 min the medulla was dissected, post-fixed in the same solution for 6 h at 4 °C, and washed overnight in 0.1 M sodium cacodylate buffer (pH 7.0) containing isotonic sodium sulfate and calcium acetate. For light microscopy, frozen sections of 25-40 #m thickness were cut. For the demonstration of butyrylcholinesterase activity the thiocholine method of Koelle 11 as modified by Khsa and Csillik 10 was performed at room temperature, at pH 5.4 using butyrylthiocholine iodide as substrate in the presence of 10 -4 M BW284C51 *. After an incubation period of 5 h the sections were rinsed in sodium cacodylate buffer (pH 7.4) and subsequently treated with a 2 %o solution of sodium sulfide, dehydrated and mounted in Canada balsam. For electron microscopy, sections of 60-80 #m thickness were obtained on a Smith-Farquhar 18 tissue chopper. Butyrylcholinesterase activity was demonstrated according to the method of Lewis and Shute 14,15 using butyrylthiocholine iodide as substrate in the presence of 10 -4 M BW284C51 at 4 °C (pH 5.4). After an incubation period of 5 h, sections were washed in succinate buffer and treated with a 2 ~ buffered solution of sodium sulfide. Sections were tr immed under a dissecting microscope,

Histochemical evidence for the role of Ca2+ and neutral protease in the development of the subacute myopathy induced by organophosphorous compounds

A temporal and causal relationship has been established between inhibition of acetylcholinesterase (AChE) by organophosphorous compounds, accumulation of Ca2+, an increase of neutral protease activity and the development of the ultrastructural signs of subacute myopathy.

Acetylcholinesterase activity of Renshaw elements and Renshaw bulbs. A light- and electron-histochemical study

SummaryRenshaw elements, representing the structural basis of spinal recurrent inhibition, consist of bulbous dilatations of the dendrites of Renshaw cells. These dendritic bulbs are surrounded by terminals derived from initial axon collaterals of motoneurons. The axon terminals display intense acetylcholinesterase activity. Light-microscopic histochemistry reveals the convergence of numerous acetylcholinesterase-positive axons on every Renshaw bulb. Electron histochemistry suggests that the central ‘core’ of the Renshaw element is in effect, a bulbous dendritic dilatation. Acetylcholinesterase activity is confined to surface membranes of terminal axons.

A LIGHT AND ELECTRON MICROSCOPIC HISTOCHEMICAL STUDY ON THE MECHANISM OF DFP-INDUCED ACUTE AND SUBACUTE MYOPATHY

Tóth L., Karcsú S., Poberai M. & Sávay Gy. (1981) Neuropathology and Applied Neurobiology 7, 399–410

Ultrastrukturelle veränderungen des supraoptico-neurohypophysären systems nach läsion des hypophysenstiels bei der ratte

Zusammenfassung Die nach elektrolytischer Zerstorung des Hypophysenstiels auftretenden ultrastrukturellen Veranderungen wurden im Nucleus supraopticus und in der Neurohypophyse untersucht. In den Nervenzellen des Nucleus supraopticus spielt sich die Chromatolyse ab. Die proliferierten Mikrogliazellen trennen die axosomatischen Synapsen ab und phagocytieren die degenerierten Neurone. In der 3. und 4. postoperativen Woche sind die morphologischen Merkmale einer Regeneration in solchen Neuronen wahrzunehmen, die die Axotomie uberlebt haben. In der Neurohypophyse beginnen der Zerfall der sekretorischen Blasehen und die Degeneration der Axonendigungen um den 3. bis 4. Tag post operationem . Die degenerierten Terminale werden von Pituicyten phagocytiert. In der 4. postoperativen Woche sind immer noch keine auf Axonregeneration hindeutenden ultrastrukturellen Zeichen in der Neurohypophyse festzustellen.

Calcium-containing mitochondrial granules in neurohypophysial axon terminals disappear following vasopressin treatment of brattleboro rats

The presence of intramitochondrial calcium-containing electron-dense granules was demonstrated in axon terminals of chronically hyperactive neurosecretory neurons of untreated homozygous Brattleboro rats. Following vasopressin treatment for 30 days, which has been shown to attenuate this neuronal hyperactivity, calcium-containing deposits could not be detected in mitochondria. It is concluded that the presence of intramitochondrial calcium-containing dense deposits is connected with the functional state of neurosecretory neurons.

Morphological evidence for the involvement of calcium in neurohypophysial hormone release

An elevated intracellular Ca2+ concentration in the secretory nerve endings of the rat neurohypophysis was detected histochemically by means of light microscopy concomitant with the vasopressin secretion evoked by hypertonic saline. The electron microscopic and X-ray microanalytical results furnish morphological evidence for the function-dependent Ca2+ storage capacity of the mitochondria, and suggest their role in the regulation of the free Ca2+ level in the neurosecretory axon terminal.

Na-Glutamat-sensitive Nervenzellen in der Area postrema bei der Ratte

Summary A single subcutaneous injection of monosodium-L-glutamate induces severe ultrastructural alterations in certain AChE positive parenchymal cells of the Area postrema of the adult rat. Signs of cellular degeneration include massive intracellular edema, swelling of mitochondria, vacuolization of the cisternae of the rough endoplasmic reticulum and marked alterations in the chromatin pattern of the nucleus. Identification of these cells as neurons is based on the presence of axosomatic synapses.