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  • 1
    Electronic Resource
    Electronic Resource
    Alterations in axons and synapses of olfactory cortex following olfactory bulb lesions in newborn rats (1980)
    Springer
    Anatomy and embryology 160 (1980), S. 153-172 
    Details
    ISSN: 1432-0568
    Keywords: Reinnervation ; Synapse development ; Olfactory system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The olfactory cortex of rats is being studied at various survival times following deafferentating olfactory bulb ablation on the day of birth. The neonatal axons and synaptic terminals undergo rapid, flocculent degeneration and fragmentation. Most are not electron-dense and therefore probably not argyrophilic at this particular age of the lesion. The degeneration and removal of debris is far more rapid than in adults, yielding a markedly enlarged extracellular space with a relative absence of glia at the vacated postsynaptic “thickenings”. Denervated postsynaptic “thickenings” become occupied by neuronal and nonneuronal profiles and profiles of uncertain origin, singly or in various combinations, or the sites may remain partially vacant. One or more axons with synaptic vesicles often aggregated at the site are commonly involved. Certain terminals form contacts on progressively greater lengths of the “thickening” until typical synaptic contacts predominate by 14 days survival. The results suggest a competitive reinnervation process and provide a fine structural explanation for the events leading to alterations in this pathway following neonatal deafferentation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00301858
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  • 2
    Electronic Resource
    Electronic Resource
    Unilateral retrogasserian rhizotomy causes contralateral degeneration in spinal trigeminal nuclei of cats: an ultrastructural study (1993)
    Springer
    Experimental brain research 93 (1993), S. 28-36 
    Details
    ISSN: 1432-1106
    Keywords: Primary afferents ; Synapse degeneration ; Deafferentation ; Trigeminal ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We are studying the response to injury within the brainstem trigeminal nucleus following trigeminal nerve lesions. We have previously shown with light microscopy and reduced silver stains that unilateral retrogasserian rhizotomy results not only in massive degeneration throughout the ipsilateral spinal trigeminal nucleus; in addition, degeneration is seen in a ventral position at the periobex region (involving caudal pars interpolaris and rostral pars caudalis) in the contralateral spinal trigeminal nucleus. In the present study, we have used electron microscopy to identify the source of the degenerating elements seen bilaterally after unilateral retrogasserian rhizotomy in eight adult felines with survival times ranging from 3 to 20 days. At short survival times (3–7 days) degenerating terminals with round synaptic vesicles (R terminals) and type 1, asymmetric contacts predominate bilaterally, while fewer degenerating terminals with flattened synaptic vesicles (F terminals) and type 2, symmetric contacts are seen. At longer survival times more F terminal degeneration is seen, especially on the contralateral side. Postsynaptic sites and dendrites show minimal alterations. These findings suggest that the degenerating R terminals seen on the contralateral side originate from primary afferents while the degenerating F terminals seen on the contralateral side originate from intrinsic sources involving a crossed internuclear pathway. In addition, the finding of degenerating F terminals may represent a novel form of selective transynaptic change of intrinsic neurons, associated with minimal dendritic or somatic alterations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227777
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  • 3
    Electronic Resource
    Electronic Resource
    Studies of the direct coloring thiocholine method for localizing cholinesterase activity (1974)
    Springer
    Histochemistry and cell biology 40 (1974), S. 13-23 
    Details
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Choline ester hydrolysis has been studied in vitro employing routine and unbuffered variations of the histochemical medium described by Karnovsky and Roots (1964) in their direct coloring thiocholine method for the localization of cholinesterase activity in situ. The substrates acetylcholine and acetylthiocholine did not hydrolyze spontaneously in either buffered or unbuffered media. However, hydrolysis of both choline esters proceeded immediately when exogenous acetylcholinesterase was present in enzyme to substrate ratios of 0.1 or less. All reactions were slower at higher enzyme to substrate ratios. Hydrolysis was prevented by including 2×10−4M eserine in the medium while 2×10−4M tetraisopropylpyrophosphoramide had no detectable effect. Butyrylthiocholine was not hydrolyzed by exogenous acetylcholinesterase in this system. Homogenates of fresh brains or brains fixed in aldehyde were equally effective in hydrolyzing acetylthiocholine in the unbuffered medium. Results of the light and electron microscopic observations confirmed other reports that acetylthiocholine in combination with the appropriate inhibitor results in a staining reaction representing cholinesterase distribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00490269
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  • 4
    Electronic Resource
    Electronic Resource
    An electron microscopic study of the normal synaptic relationships and early degenerative changes in the rat olfactory tubercle (1972)
    Springer
    Cell & tissue research 127 (1972), S. 462-482 
    Details
    ISSN: 1432-0878
    Keywords: Olfactory tubercle ; Rat ; Degeneration ; Synapse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The olfactory tubercle of the rat was studied by electron microscopy both in the normal and after ipsilateral olfactory bulb ablation at survival times of from 14 hours to seven days. Particular emphasis was placed on synaptic structures and their changes following the lesion. Normal synapses are similar to those described in previous studies and presynaptic profiles are of at least three types. Types-A and -B contain round vesicles and form asymmetrical contacts and type-C profiles contain flattened vesicles and form symmetrical contacts. There appear to be two major types of degenerative changes. The electron-lucent type predominates at early survival times and is seen first at 14 hours. These profiles show an early reduction in numbers of vesicles with mitochondrial swelling followed by shrinkage of the profile. These profiles become increasingly electron-dense at later survival times. The second major type of degenerating profile is initially electron-dense. The earliest changes in these profiles are an increased axoplasmic density and increased microtubular density and clumping without apparent loss of vesicles. These profiles also become progressively more electron-dense at longer survival times. The observations are discussed in relation to previous reports.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00306866
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  • 5
    Electronic Resource
    Electronic Resource
    Independent development of presynaptic specializations in olfactory cortex of the fetal rat (1984)
    Springer
    Cell & tissue research 237 (1984), S. 103-109 
    Details
    ISSN: 1432-0878
    Keywords: Synapses ; Synaptogenesis ; Development fetal ; Olfactory cortex ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Electron microscopy was used to study synaptogenesis in prepyriform cortex of fetal rat pups during early stages of synapse formation. Of special interest is the frequent occurrence of unapposed, developing synaptic specializations in axon and growth cone profiles. The location and morphology of the unapposed specializations suggests that thay are presynaptic in nature. These presumably immature presynaptic specializations are found in the lateral olfactory tract and subjacent cortex. Intermediate forms between uncontacted presynaptic specializations and definitive synapses suggest a synaptogenic sequence in which initial development of an immature presynaptic specialization begins without apposition of a postsynaptic element at that location. This implies that initiation of presynaptic development is not dependent upon postsynaptic contact and also raises the question of whether synaptic contacts could be established via presynaptic induction of postsynaptic formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229204
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  • 6
    Electronic Resource
    Electronic Resource
    Electron microscopy of synaptic structures in olfactory cortex of early postnatal rats (1975)
    Springer
    Journal of neurocytology 4 (1975), S. 713-732 
    Details
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Layer 1 of the rat olfactory cortex has been studied with the electron microscope at birth and at several consecutive postnatal days up to 14 days of age. Special attention was directed towards synaptic structures and axons of the lateral olfactory tract (LOT). Numerous mature synapses are seen at birth and estimates were made of their subsequent increase in number. In addition, immature synapses are seen and mature postsynaptic sites occur with atypical, partial, multiple or no contact. The findings suggest: (1) considerable prenatal synaptogenesis in contrast to other cortical systems; (2) the maturation of the postsynaptic site may precede that of the presynaptic contact and vesicle accumulation; (3) there may be competition by more than one process for one postsynaptic specialization; (4) the non-innervated sites may result from deafferentation caused by prenatal cell death, although no degeneration was seen, and the atypical contacts may be a stage in the reinnervation of these sites; (5) the LOT develops in parallel with the synaptic neuropil and (6) by 14 days of age the area closely resembles adult tissue.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01181632
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  • 7
    Electronic Resource
    Electronic Resource
    Acetylcholinesterase activity of synaptic structures in the spinal trigeminal nucleus (1976)
    Springer
    Journal of neurocytology 5 (1976), S. 551-563 
    Details
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The electron microscope has been used to study the localization of acetylcholinesterase (AChE) activity in the spinal trigeminal nucleus of normal cats with special emphasis on the distribution near synaptic structures. Reaction product is found around both round and flattened synaptic vesicle-containing axon terminals, particularly in synaptic clefts and often specifically associated with the presynaptic, or less frequently the postsynaptic membrane. The presence of reaction product at these specific sites suggests that these are areas of high AChE activity and that acetylcholine may be important in neurotransmission in these regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01175569
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  • 8
    Electronic Resource
    Electronic Resource
    Ultrastructure of degenerative changes following ricin application to feline dental pulps (1987)
    Springer
    Journal of neurocytology 16 (1987), S. 601-611 
    Details
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The ultrastructure of degenerative changes within the ipsilateral trigeminal ganglion, and partes caudalis and interpolaris of the spinal trigeminal nucleus in the cat is described following the application of the potent toxin ricin to the tooth pulps of unilateral maxillary and mandibular posterior teeth, including the cuspids. Survival times ranged from 6 to 10 days. Typical changes identified within the ipsilateral trigeminal ganglion included myelin fragmentation and ‘compartmentalization’ of the axoplasm of medium-sized myelinated axons, while small myelinated and unmyelinated axons underwent a more variable response ranging from electron-lucent to electron-dense changes. The affected cell body was characterized by the presence of swollen, electron-lucent mitochondria, a reduction of cytoplasmic ribosomes and a filamentous hyperplasia. Other changes often included an eccentric nucleus and satellite cell proliferation. Degenerative changes often occurred in isolated elements surrounded by normal profiles, suggesting specificity of ricin within the trigeminal ganglion. Changes within brainstem axons showed both an electron-dense and a lucent, fragmenting type of axonal alteration. Terminal changes ranged from electron-dense to lucent and also included filamentous hyperplasia and ‘hyperglycogenesis’. The altered axonal knobs contained round synaptic vesicles that were presynaptic to dendritic profiles and postsynaptic to terminals containing flattened synaptic vesicles. The above brainstem alterations were identified specifically in the following areas: ventrolateral, medial and dorsomedial pars interpolaris; the ventrolateral and mid-dorsal to dorsomedial areas of the marginalis and outer substantia gelatinosa layers of pars caudalis; and in ventral pockets corresponding to lamina V of the medullary dorsal horn. Dense alterations within terminals containing flattened synaptic vesicles that are typically presynaptic to primary afferents in these areas were rare findings, but along with vacuolization of dendritic profiles suggest a trans-synaptic effect possibly due to the exocytosis of ricin. The results are discussed in relation to different reports of dental projections and with regards to patterns of transganglionic degeneration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01637653
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  • 9
    Electronic Resource
    Electronic Resource
    Early forms of terminal degeneration in the spinal trigeminal nucleus following rhizotomy (1973)
    Springer
    Journal of neurocytology 2 (1973), S. 189-215 
    Details
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Pars interpolaris of the spinal trigeminal nucleus in adult cats has been studied with the electron microscope at several early and consecutive postoperative survival times following retrogasserian rhizotomy. The results show that several different forms of degenerative changes occur in the axon terminals and some of these forms may be interpreted as stages in certain sequences of terminal degeneration. Synaptic vesicle depletion and mitochondrial alterations are probably the earliest changes in some terminals, but the occurrence of completely different forms also at very early survival times suggest that other processes may be involved. Electron-dense forms of terminal degeneration of later survivals are suggested as arising from any of at least four possible types or classes of earlier alterations based upon presence or absence of vesicles and neurofilaments and on the mitochondrial changes. Electron-lucent forms probably progress to dense types with time but may account for only a proportion of the later dense forms. All types of neuroglia, or reactive glia, and a possible ‘third glia’ are involved in early and rapid phagocytosis and denudation of post-synaptic sites at times earlier than previously reported. The study also confirms a previous study of a time-related degeneration pattern in the same area and offers an explanation for this pattern.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01474720
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  • 10
    Electronic Resource
    Electronic Resource
    Electron microscopy of degeneration in the lateral olfactory tract and plexiform layer of the prepyriform cortex of the rat (1969)
    Springer
    Cell & tissue research 98 (1969), S. 157-187 
    Details
    ISSN: 1432-0878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The synaptic organization of the plexiform layer of the prepyriform cortex in the rat has been studied with the electron microscope both in the normal and after ipsilateral olfactory bulb removal. Survival times ranged from six hours to three months. In normal preparations synaptic contacts occur mainly on dendritic branches, spines or lateral projections. Gray's Type I contacts are most frequent and Type II contacts usually contain flattened vesicles after formalin fixation. Degeneration of the presynaptic bags begins within 24 hours after the lesion and some degenerated bags are still seen after three months survival. During this time degenerated bags are apparently removed by astroglia but the spine tips appear to be unaffected by the phagocytosis. Glia or other processes may come to occupy the denervated sites. The evidence for possible reestablishment of new contacts is considered. The severed axons show a characteristic mode of degeneration and at three months some appear to be phagocytosed by oligodendroglia which also contain lamellated inclusion bodies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00338323
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