Morphological changes of the terminations of afferent pathways in a neurodegenerative lesion induced by kainic acid

30 days after kainic acid injection into the rat ventrobasal thalamus, lemniscal afferents were labeled using wheat-germ agglutinin conjugated to HRP. They appeared considerably swollen in the area where neuronal post-synaptic targets had been eliminated. Electron microscopic analysis of the lesioned tissue revealed the presence of large profiles containing numerous organelles, particularly smooth endoplasmic reticulum, and giving rise to thin excrescences filled with neurofilaments. Since these morphological features are typical of regenerating "growth cones", we conclude that afferent terminals deprived of their post-synaptic targets undergo morphological changes preparing them for new synapses.     

Electron microscopy of the arcuate nucleus of normal and 5-hydroxydopamine treated cats

The arcuate nucleus of normal cats and of cats treated with 5-hydroxydopamine (5-OHDA) was investigated by electron microscopy. The neurons of the arcuate nucleus were classified into three types, clear, intermediate and dark, according to their fine structure. The clear type contained numerous dense-cored vesicles and well developed cell organelles. All three types were frequently seen to be partially surrounded by glial processes. Many axo-somatic and axo-dendritic synapses mostly small in diameter were also observed around the neurons. Synaptic contacts were demonstrated between axon endings and axonal processes which contained elementary granules. After administration of 5-OHDA small and large dense-cored vesicles appeared in the nerve endings surrounding the neurons. The relationship between the dense-cored vesicles in the perikarya and dopamine was briefly discussed.     

Effect of social isolation on the ultrastructure of the dog brain

Ultrastructural changes in the central nucleus of the amygdalar body, field CA I of the hippocampus, piriform cortex, field 17 and field 7 have been studied in dogs, bred under conditions of social isolation. The changes are more numerous in emotiogenic structures. Similar ultrastructural rearrangements are revealed in the amygdalar body, hippocampus and in both fields of the neocortex. They are: neurons with different degree of chromatolysis, reactive changes in some organelles, terminals with agglutinated vesicles, or with their reduced number, increasing amount of synapses with a short active zone. At the same time, in the piriform gyrus vacuoles, membrane-like and osmiophilic inclusions, terminals with granular vesicles of various size are found more often.     

The postnatal development of the hypoglossal nucleus in the rat]

Using light and electron microscopy the neurons, glial cells and capillaries in hypoglossal nucleus of the rats have been examined up to 20 days after birth. The neuronal nuclei are usually situated ecentrically. The mitochondria and extensively developed Golgi-zones occupy the perinuclear region. The microtubules and lysosomes become more numerous with aging. At the earliest periods rough endoplasmic reticulum (ER) occupies the neuronal periphery, whereas after 14th day it is extended to the perinuclear region also. The ER forms elongated and concentric lamellated bodies and subsurface cisternae. At this time nucleolus like bodies are also numerous in the cytoplasm. After 4th and 6th days the extensive growth of dendrites, containing many cell organelles, and axons rich in microtubules are observed. Only at the birthday do neurons contain glycogen deposit. After 1st day the glycogen leaves the pericaryon, but it persists a long time in the neuronal processes. The symmetrical and asymmetrical contacts are characteristic for the examined period. The axo-somatic and axo-dendritic synapses are more abundant, but "double synapses" are also established. More synaptic boutons possess besides synaptic vesicles dense-core vesicles at the earlier periods. The quantity of asymmetric synapses increases with differentiation. Extensive cell degeneration has been established between 8 and 18th days. At 4 and 6 days the glial cells penetrate from subependymal layer and they have satellite neuronal position. This is more pronounced between 14 and 18 days when the oligodendrocytes are more numerous and active. At the same time fibrous astrocyte like cells are appeared. Microglial cells were not observed. Capillary differentiation, expressed by changes of the endothelial cells, pericytes and connective tissue cells, continues after birth also.     

Correlation between rotational behaviors and neurochemical changes associated with damage of rat striatum: Analysis using unilateral microinjection of kainic acid

The correlation between rotational behaviors and neurochemical changes associated with the striatal damage induced by an unilateral microinjection of kainic acid were investigated. Shortly after the unilateral striatal injection of kainic acid, rats exhibited contralateral rotational behaviors, and these changes were antagonized by the simultaneous striatal injection of haloperidol. On the other hand, systemic injection of methamphetamine to animals having the lesion on nigro-striatal dopaminergic neurons exhibited ipsilateral turnings. In addition, it was found that the release of [¹⁴C]dopamine from striatal slices was increased by the in vitro addition of kainic acid. Following 2 days after the striatal injection of kainic acid and thereafter, the rats exhibited ipsilateral rotational behaviors and microinjection of muscimol into the ipsilateral substantia nigra of these animals altered turning movements to a contralateral type. Simultaneous nigral injection of bicuculline antagonized to the muscimol-induced contralateral turnings. These results suggest that the increase of dopamine release from dopaminergic neurons in the striatum may be involved in the occurrence of contralateral turning behaviors observed shortly after the striatal kainic acid treatment. The present results also suggest that changes in the functional states of striatonigral GABA-ergic neurons may play an important role in the occurrence of ipsilateral rotational movements at a late stage following the striatal injection of this agent.     

Ultrastructure of orexin-1 receptor immunoreactivities in the spinal cord dorsal horn

The ultrastructural properties of orexin 1-receptor-like immunoreactive (OX1R-LI) neurons in the dorsal horn of the rat spinal cord were examined using light and electron microscopy techniques. At the light microscopy level, the most heavily immunostained OX1R-LI neurons were found in the ventral horn of the spinal cord, while some immunostained profiles, including nerve fibers and small neurons, were also found in the dorsal horn. At the electron microscopy level, OX1R-LI perikarya were identified containing numerous dense-cored vesicles which were more heavily immunostained than any other organelles. Similar vesicles were also found within the axon terminals of the OX1R-LI neurons. The perikarya and dendrites of some of the OX1R-LI neurons could be seen receiving synapses from immunonegative axon terminals. These synapses were found mostly asymmetric in shape. Occasionally, some OX1R-LI axon terminals were found making synapses on dendrites that were OX1R-LI in some cases and immunonegative in others. The synapses made by OX1R-LI axon terminals were found both asymmetric and symmetric in appearance. The results provide solid morphological evidence that OX1R is transported in the dense-cored vesicles from the perikarya to axon terminals and that OX1R-LI neurons in the dorsal horn of the spinal cord have complex synaptic relationships both with other OX1R-LI neurons as well as other neuron types.     

The nucleus of the basal optic root in the pigeon: an electron microscope study

The ultrastructure of the nucleus of the basal optic root in an avian species (Columba livia) was investigated. The ectomamillary nucleus (EMN) in which terminates the basal optic tract reveals three types of neurons: 1) small round neurons bearing a scanty cytoplasm in organelles, 2) medium-sized neurons, spindle-shaped with a dense population of organelles and 3) large multipolar neurons with well developed perikaryal elements. Some of these neurons have their inner plasma-membrane which fuse to make junctional zones alternating between attachment plates and gap junctions. The analysis of the neuropil displays four types of vesicle-containing profiles (VCP), Type I VCP, identified as optic terminals, are numerous (49%), contain round vesicles (500-550 A) and establish Gray type I contacts principally with dendrites. They also participate in serial and triadic arrangements. Type II VCP have lighter hyaloplasm and are less numerous (6,7%). Rounded vesicles (450-500 A) with a clear content synapse also with Gray type I active zones on dendrites. Some of these profiles have the peculiarity of both a chemical and electrical transmission known as mixed synapses. Type III VCP are larger and contain a mixed population of rounded and flattened vesicles which synapse according to Gray type II. Type IV VCP are characterized by a light hyaloplasm where the microtubules are a predominant organelle. Their active zones are also of Gray type II.     

The Protective Effect of Myo-inositol on Hippocamal Cell Loss and Structural Alterations in Neurons and Synapses Triggered by Kainic Acid-Induced Status Epilepticus

It is known that myo-inositol pretreatment attenuates the seizure severity and several biochemical changes provoked by experimentally induced status epilepticus. However, it remains unidentified whether such properties of myo-inositol influence the structure of epileptic brain. In the present light and electron microscopic research we elucidate if pretreatment with myo-inositol has positive effect on hippocampal cell loss, and cell and synapses damage provoked by kainic acid-induced status epilepticus. Adult male Wistar rats were treated with (i) saline, (ii) saline + kainic acid, (iii) myo-inositol + kainic acid. Assessment of cell loss at 2, 14, and 30 days after treatment demonstrate cytoprotective effect of myo-inositol in CA1 and CA3 areas. It was strongly expressed in pyramidal layer of CA1, radial and oriental layers of CA3 and in less degree—in other layers of both fields. Ultrastructural alterations were described in CA1, 14 days after treatment. The structure of neurons, synapses, and porosomes are well preserved in the rats pretreated with myo-inositol in comparing with rats treated with only kainic acid     

Reversible ultrastructural changes of arcuate neurons after vinblastine injection into the median eminence of the rat

Summary The ultrastructural effects of vinblastine on the arcuate neurons and median eminence were studied in the rat. The animals were stereotaxically injected with solutions of 1 mM and 5 mM vinblastine into the median eminence and killed 3, 8 and 21 days after injection. Eight days after injection of 1 mM vinblastine the neurons of the arcuate nucleus showed marked changes. The Golgi complex was more distinct and considerable increases in the populations of dense bodies, granulated vesicles and coated vesicles were observed. Changes in the axo-somatic synapses and degenerating fibers in the surrounding neuropil were also characteristic of the experimental animals. The outer zone of the median eminence showed numerous degenerated nerve fibers and fibers engulfed by glial cell processes. Eight days after injection of 5 mM vinblastine arcuate neurons and median eminence showed similar changes, but quantitative differences were noted. A striking ultrastructural recovery of the arcuate neurons and axons in the outer zone of the median eminence was observed 21 days after injection of either 1 mM or 5 mM vinblastine. The results are discussed in relation to axoplasmic transport and axonal degeneration.Supported by CONICET and National University of Cuyo, Argentina.Members of the Scientific Research Career of the Consejo Nacional de Investigaciones Cientificas y Tecnicas, Argentina.     

Morphological changes in the hippocampus following nicotine and kainic acid administration

Using histochemical analysis (NADPH-diaphorase, Fluoro-Jade B dye and bis-benzimide 33,342 Hoechst) we studied the influence of intraperitoneal administration of nicotine (NIC), kainic acid (KA) and combination of both these substances on hippocampal neurons and their changes. In experiments, 35-day-old male rats of the Wistar strain were used. Animals were pretreated with 1 mg/kg of nicotine 30 min prior to the kainic acid application (10 mg/kg). After two days, the animals were transcardially perfused with 4 % paraformaldehyde under deep thiopental anesthesia. Cryostat sections were stained to identify NADPH-diaphorase positive neurons that were then quantified in the CA1 and CA3 areas of the hippocampus, in the dorsal and ventral blades of the dentate gyrus and in the hilus of the dentate gyrus. Fluoro-Jade B positive cells were examined in the same areas in order to elucidate a possible neurodegeneration. In animals exposed only to nicotine the number of NADPH-diaphorase positive neurons in the CA3 area of the hippocampus and in the hilus of the dentate gyrus was higher than in controls. In contrast, KA administration lowered the number of NADPH-diaphorase positive cells in all studied hippocampal areas and in both blades of the dentate gyrus. Massive cell degeneration was observed in CA1 and CA3 areas of the hippocampus and in the hilus of the dentate gyrus after kainic acid administration. Animals exposed to kainic acid and pretreated with nicotine exhibited degeneration to a lesser extent and the number of NADPH-diaphorase positive cells was higher compared to rats, which were exposed to kainic acid only.     

Effect of hypokinesia on the ultrastructure of emotion-controlling structures in the rat brain

Hypokinesia lasting 40 and 90 days causes a number of ultramicroscopic reorganizations in neurons, synapses and glial elements of the singular cortex and the central amygdaloid nucleus. The longer the time of hypokinesia, the more numerous and variable the reorganizations become. For the amygdaloid body presence of neurons with various degree of chromatolysis, reactive and destructive changes of organells, agglutination and reduction in number of the synaptic vesicles, increasing number of synapses, possessing certain features of low functional activity are most specific. For the singular cortes are peculiar convolution of nuclear and cellular membranes, synaptic contact, increasing intercellular spaces, as well as changes in the structure of some axo-spine synapses, the spine apparatus including.     

Characterization of orexin A immunoreactivity in the rat area postrema

The distribution of orexin A immunoreactivity and the synaptic relationships of orexin A-positive neurons in the rat area postrema were studied using both light and electron microscopy techniques. At the light microscope level, numerous orexin A-like immunoreactive fibers were found within the area postrema. Using electron microscopy, immunoreactivity within fibers was confined primarily to the axon terminals, most of which contained dense-cored vesicles. Both axo-somatic and axo-dendritic synapses made by orexin A-like immunoreactive axon terminals were found, with these synapses being both symmetric and asymmetric in form. Orexin A-like immunoreactive axon terminals could be found presynaptic to two different immunonegative profiles including the perikarya and dendrites. Occasionally, some orexin A-like immunoreactive profiles, most likely to be dendrites, could be seen receiving synaptic inputs from immunonegative or immunopositive axon terminals. The present results suggest that the physiological function of orexin A in the area postrema depends on synaptic relationships with other immunopositive and immunonegative neurons, with the action of orexin A mediated via a self-modulation feedback mechanism.     

Some factors influencing the neurotoxicity of intrastriatal injections of kainic acid

Intrastriatal injections of kainic acid are known to destroy striatal neurons including many containing choline acetyltransferase (CAT) and glutamic acid decarboxylase (GAD). Using these enzymes as indices of neuronal loss, the neurotoxicity of small doses of kainic acid was found to be influenced by injection time and volume. It was partly blocked by coninjection of some but not all glutamate antagonists or by prior lesioning of the corticostriatal tract. Other adjuvants, drugs, or lesions tested had little modifying effect, except that changes in the dopaminergic system seemed to increase the toxicity towards cholinergic but not GABAnergic systems. High-affinity glutamate accumulation by neostriatal synaptosomes was significantly increased 1–7 days following kainic acid injections. MAO and acetylcholinesterase activities were depressed in kainic acid-lesioned striata but not nearly as much as were CAT and GAD. An indirect mechanism involving glutamate release and inhibition of reuptake is suggested for kainic acid neurotoxicity.     

Effect of short-term starvation on the cells of the proximal convoluted tubule of the mouse: a cytological and cytochemical study

Synopsis The effects of starvation on the intracellular distribution of acid glycerophosphate phosphatase have been studied in the cells of the proximal convoluted tubule of mouse kidney. Severe cytological and cytochemical changes begin in the cell two hours after withdrawal of food. They consist primarily in the appearance of numerous acid phosphatase-positive cytoplasmic vesicles arising from a hypertrophy of the rough endoplasmic reticulum. This is followed by the appearance of numerous acid phosphatase-positive Golgi zones and by degenerative changes of the mitochondria. After eighteen hours the cells also contain a large number of droplets of nonosmiophilic material, probably neutral fats, sited mainly in the area of the basement membrane, some cytosegresomes and several residual bodies sited below the brush border in the apical region of the cells. Since there appears to be a lack of correlation between the number and time of appearance of the cytosegresomes, the time of appearance and intensity of the reaction for nonlysosomal acid phosphatase, and the entity of cellular damage, this has led the authors to suggest the possibility that, beside the lysosomal autophagy described by other workers, there may occur in these experimental circumstances also a direct digestion of subcellular organelles by the acid phosphatasepositive vesicles of the rough endoplasmic reticulum, and that this mechanism may explain the formation of lipid droplets.     

Characterization of specific in vivo binding of neuroleptic drugs in rat brain.

Lesioning of the rat striatum with kainic acid may provide a useful animal model with which to study Huntington's Disease since, in both situations, changes in several neurochemical parameters appear similar. In this study, we examined the time course of dopaminergic (DA) and muscarinic cholinergic (MCHOL) receptor alterations after kainic acid injection into the rat striatum. As early as two days after unilateral, intrastriatal injection of kainic acid, most striatal perikaya in the injected area had been destroyed as seen by histological examination. A progressive decrease in the DA and MCHOL receptors continued which was not due to changes in their affinity for their respective receptors. By 48 days after injection, there was about 75% decrease in DA receptors and about a 65% decrease in MCHOL receptors. The DA receptor loss is similar in extent to the reported loss in activity of striatal, dopamine-stimulated adenylate cyclase after kainic acid lesion. The DA and MCHOLreceptor loss is similar to the reported loss of neostriatal DA and MCHOL receptors in Huntington's Disease.     

Morphological and Biochemical Changes in the Cerebellum Induced by Kainic Acid In Vivo

Abstract: Injection Of nanomole quantities Of kainic acid into The Rat cerebellum resulted in a rapid and selective destruction Of neurons. At all times Studied, the purkinje cells were depleted following injection, and this loss was paralleled by a decrease in GABA levels, high-affinity neuronal GABA uptake, and in glutamate decarboxylase activity. For the first 3 days following injection The granule cells were not reduced in numbers and the high-affinity uptake of glutamate was similarly not decreased. After 4-6 days, however, the granule cells were substantially depleted, although No clear changes in glutamate up-take were observed. The normal laminar structure of the cerebellum was extensively disrupted and glial proliferation was evident. Measurement of endogenous amino acid levels showed a decrease in glutamate and aspartate levels after kainic acid injection. glycine levels were consistently increased while glutamine and alanine were unchanged. GABA receptor binding was decreased after injection, but glutamate binding was enhanced.     

Possible destruction of cholinoceptive neurons by overstimulation of cholinergic tracts

It is well established that intracerebral injections of kainic acid may cause not only neuronal cell destruction at the injection site, but also losses in some distant regions. The mechanisms are different. The distant, but not the local, destruction can be produced by folic as well as by kainic acid and prevented by pretreatment of the animal with diazepam. Overexcitation of excitatory projections is believed responsible for the distant damage and evidence is presented that in some instances the projections involved are cholinergic. Thus, for example, injections of kainic acid or folic acid into the substantia innominata of rats destroy neurons in areas such as the pyriform cortex and amygdala which receive cholinergic projections from the injected area. Some of the destroyed neurons are GABAergic. That the distant toxicity in these areas can be partially blocked by scopolamine and is accompanied by decreases in the number of muscarinic binding sites is consistent with a cholinergic mechanism. Distant damage also occurs in the thalamus but this appears to be mediated by a noncholinergic projection. Similar injections of folic acid or kainic acid into the rostral pontine tegmentum, another area with cholinergic cells, cause destruction of both dopaminergic and GABAergic neurons in the substantia nigra. The effect on the GABAergic but not that on the dopaminergic cells is blocked by scopolamine. The results are discussed in relation to possible mechanisms of epilepsy and of selective neuronal losses in diseases such as Parkinson's disease.     

Concanavalin A-Induced Morphological Changes and Its Binding Sites in Starfish Follicle Cells as Revealed by Electron Microscopy

Concanavalin A (Con A) stimulates the production in starfish follicle cells of 1-methyladenine, a hormone which induces oocyte maturation. We have therefore investigated Con A-induced morphological changes and Con A-binding sites in the follicle cell using native Con A and horseradish peroxidase- or ferritin-labeled Con A (HRP-Con A, Fer-Con A). After isolated follicle cells were incubated with Con A (1 mg/ml), vacuoles, the Golgi complex and multivesicular body-like organelles (MVBs) became prominent in most of the cells. After follicle cells were prefixed and then incubated with Fer-Con A for 60 min, tagged ferritin was diffusely and randomly distributed as single or small clustered particles on the cell surface. The incubation of isolated follicle cells with Fer-Con A for 10 min before fixation resulted in numerous ferritin particles localized along the internalized membrane, and also in vacuoles, MVBs and small lysosome-like structures. After 60 min incubation with Fer-Con A, ferritin was further located in large lysosome-like structures and in vesicles near and in the Golgi area as well as in the organelles described above. HRP-Con A binding sites were also observed in vacuoles and MVBs of the intact cells.
These results suggest that Con A binds at first to the cell surface and causes rapid internalization and that membrane-bound Con A is easily endocytosed into vacuoles, MVBs and lysosome-like structures, and is later incorporated in some vesicles in the Golgi area.     

Ultrastructure and morphometric parameters of glutamatergic synapses on nigrothalamic and unidentified neurons of the reticular zone of theSubstantia nigra in cats

Nigrothalamic neurons were identified into thesubstantia nigra by their retrograde labelling with horseradish peroxidase. Axon terminals that contain glutamate (the excitatory transmitter) were revealed immunocytochemically with an immunogold electron microscopic technique. Ultrastructural parameters (the large and small diameters of axon terminals, area of their profiles, coefficient of form of profiles, large and small diameters of synaptic vesicles) were analyzed in all 240 synapses under study. Synaptic contacts localized on both nigrothalamic and unidentified neurons belonged to three morphologically specific groups. Synapses of the groups I and III, according to classification by Rinvik and Grofova, were characterized by a symmetric type of synaptic contact and contained polymorphic synaptic vesicles. Contacts in group-II synapses were asymmetric, and respective terminals contained round vesicles. Among the studied synapses, 65.8% were classified as group-I contacts, 25.0% belonged to group II, and 9.2% belonged to group III. Glutamate-positive axon terminals formed predominantly group-II synapses; such connections constituted 70% of this group's synapses. Sixty percent of glutamate-positive synapses were localized on the distal dendrites and 23% on the proximal dendrites, while 17% of such synapses were distributed on the somata of nigral neurons. Such a pattern of distribution of glutamate-positive synapses was observed on both nigrothalamic and unidentified nigral neurons. About 7% of glutamate-positive synapses were formed by very large axon terminals containing round synaptic vesicles; yet, the contacts of these terminals were of a symmetric type. Twenty percent of group-I synapses, i.e., synapses considered inhibitory connections, were found to manifest a weak immune reaction to glutamate.Neirofiziologiya/Neurophysiology, Vol. 28, No. 6, pp. 285–295, November–December, 1996.