A.M. Adinolfi

Segmental demyelination in peripheral nerves of old cats

This study of the fine structure of sciatic nerve branches in normal old cats provides evidence indicating that segmental demyelination may account, in part, for the significant decrease with age in the mean axonal conduction velocity in these hindlimb nerves. Fibers of different diameters exhibited focal abnormalities of their myelin sheath. Lipid-like droplets and granulo-vacuolar debris were present in distended portions of the inner adaxonal rim and in the outer cytoplasmic compartment of the Schwann cell. These inclusions extended into the cytoplasm of the paranodal myelin loops and clefts of Schmidt-Lantermann. There also occurred disruption of the axoglial junctions and separation of the myelin loops from the paranodal axolemma which widens the nodes of Ranvier. Complete disruption of one or more contiguous segments of the myelin sheath was produced by interlamellar splitting and ballooning along the major dense and intraperiod lines. Axonal degeneration occurred less frequently and was not present in all hindlimb nerves.

Projections to the neostriatum from the cat precruciate cortex. Anatomy and physiology

The projections to the striatum from two cytoarchitectonically and functionally distinct subdivisions of the cat precruciate motor cortex were studied using anatomical and electrophysiological techniques. Our results indicate that the medial precruciate cortex (stimulation of which leads to movements of the axial and proximal musculature) has a widespread projection to the lateral half of the caudate nucleus. The lateral precruciate cortex (stimulation of which leads to movements of the distal musculature) has a localized projection within the caudate nucleus adjacent to the internal capsule. Both medial and lateral precruciate areas project to the putamen. These results are discussed in relation to recent studies suggesting that the basal ganglia are involved in the enabling and sequencing of movements.

The postnatal development of the caudate nucleus: a golgi and electron microscopic study of kittens

This study used light and electron microscopy to describe changes in the synaptic organization of developing caudate nucleus and to quantitate postnatal synaptogenesis in this region. Observation at the light microscopic level focus on the perinatal period and suggest an early maturation of spiny interneurons of the caudate nucleus. Golgi impregnation of these cells at early postnatal ages (birth to 7 days) reveals 3-5 primary dendrites which radiate from the cell body and extend for distances of 8-16 micron before branching. Secondary dendritic branches contain spines and extend, with further branching, for additional distances of 60-160 micron. The dendritic fields of neighboring caudate neurons overlap and the axons which arise from these cells course and branch within the dendritic fields. Examination of perinatal caudate neuropil (birth to 5 days) by electron microscopy reveals an extensive and well-developed axodendritic connectivity. Axonal profiles form multiple synapses en passant along single dendrites and dendritic spines or on several adjacent dendritic branches. At these ages, terminals contain few synaptic vesicles and synaptic junctions are slightly asymmetrical. By the fifteenth postnatal day, boutons are filled with vesicles, junctional complexes are distinctly asymmetrical, and axondendritic connectivity has been modified by the increase of dendritic spines and branchlets. Thus, the basic pattern underlying the organization of synapses in the mature caudate nucleus, is established within the first week postpartum and subsequent changes are primarily quantitative.

Age-dependent changes in cat masseter nerve: an electrophysiological and morphological study

The present study was undertaken to determine the manner in which aging affects the function and structure of the masseter nerve in old cats. Electrophysiological data demonstrated a significant decrease in the conduction velocity of the action potential in old cats compared with that observed in adult cats. Light microscopic analyses revealed an age-dependent decrease in axon diameter. Electron microscopic observations of the masseter nerve in the aged cats revealed a disruption of the myelin sheaths and a pronounced increase in collagen fibers in the endoneurium and perineurium. These morphological changes are discussed and then related to the decrease in conduction velocity which was observed in the electrophysiological portion of this study.

Quantitative morphology of medium-sized caudate spiny neurons in aged cats

These studies were designed to assess some of the morphological alterations that occur in medium-sized spiny neurons of the caudate nucleus in aged cats. Computer assistance was used to quantify in three dimensions the extent of the dendritic trees of 164 neurons from 11 cats (5 1-3 years and 6 over 10 years of age) stained by the rapid Golgi technique. In all animals beyond 10 years of age there was a decrease in the density of spines on distal dendritic segments. This decrease was moderate (16%) in 13 year old cats and reached about 50% in 15 and 18 year old animals. In addition, there was an increase in the frequency of occurrence of spines with enlarged heads in all aged cats. In cats over 13 years there was a marked loss of portions of distal dendritic segments. All measures of dendrite length displayed statistically significant decreases of 30-40% in cats 15 and 18 years of age. There were no significant age-related alterations in numbers of dendrites, number of branches per dendrite or soma diameter. These morphological results indicate that there is a sequence of age-related changes that occurs in caudate medium-sized spiny neurons and provides a basis from which to assess functional alterations.

Cytochemical localization of cyclic nucleotide phosphodiesterase activity at developing synapses

Summary Cyclic 3′,5′-nucleotide phosphodiesterase (PDE) activity has been localized cytochemically in the molecular layer of developing cerebral corte.. During the first postnatal month, reaction product is found consistently at emerging postsynaptic sites along developing dendrites. Formation of this reaction product is inhibited by the addition of theopylline to the incubation medium. Demonstration of PDE activity during development suggests that certain immature receptor sites are capable of cyclic AMP metabolism. Such sites may be related in part to monoaminergic pathways developing in the superficial neocortex.

Development of the kitten substantia Nigra: A rapid golgi study of the early postnatal period

The rapid Golgi method was used to describe the morphological maturation of substantia nigra (SN) neurons and the surrounding afferent axons. Observations were made from 25 kittens grouped at 1-3, 7-10, 18-24, and 40-55 days of age. Although variability in dendritic development among neurons is seen at each age, a common maturational sequence can be defined. The dendritic shafts at 1-3 and 7-10 days exhibit prominent varicosities and thin filiform processes along their shafts, and growth cones at their tips. The dendrites at 18-24 days are longer, thicker, and have more regular contours proximally, while varicosities and filiform processes persist distally. Neurons in this age group display shorter, spine-like processes although adult cells are known to lack typical spines. By 40-55 days, most dendritic surfaces are smooth with only scattered appendages distally. Computer-assisted measurements of dendritic growth in pars compacta neurons demonstrate a 42% increase in dendritic lengths. The number of dendrites per neuron and the number of branches per dendrite do not change between the youngest and oldest age groups. The afferent connectivity in the kitten SN is en passant in character. Two axonal types are identified at all ages. Most prominent is a thin fiber with irregularly spaced varicosities and terminal expansions 1 micron in diameter. These swellings correspond, most likely, to the type I terminals described ultrastructurally and shown to be neostriatal in origin. The second axonal type is thicker, with branches that end in clusters of enlargements, 1-2 microns in diameter. The origin of this second type is unknown.

Degenerative changes in the entopeduncular nucleus following lesions of the caudate nucleus: an electron microscopic study.

Abstract Degenative changes in the entopeduncular nucleus which result from discrete lesions of the head of the caudate were examined by electron microscopy. By the third postoperative day, numerous dense and shrunken boutons make contact with dendritic profiles in the neuropil. Few degenerated axosomatic synaptic contacts are found. Astrocytic processes isolate and presumably phagocytose degenerated boutons during the first week. Later degeneration involves mainly thin myelinated and unmyelinated axons. This is characterized by increased density and granularity of the axoplasm and myelin disruption. Contralateral entopeduncular elements remain intact following unilateral destruction of the caudate nucleus. I suggest that the inhibitory influences of the caudate nucleus on entopeduncular elements are mediated by thin, finely-myelinated and unmyelinated projections which terminate mainly on dendritic profiles in the entopeduncular nucleus.

Ultrastructural alterations in caudate nucleus in aged cats

These studies provide information on the changes in the ultrastructure in the caudate nucleus of aged cats. The major finding was that there was a decrease in the density of synapses in caudate neuropil. This decrease occurred in animals after 3 years of age and remained relatively constant in older animals. In conjunction with this change a population of unusually long synapses also occurred. These larger synaptic appositions were associated with enlarged spine heads. The caudate also showed a number of qualitative ultrastructural alterations. Many neurons contained accumulations of lipofuscin or lipopigment granules in aged animals. These inclusions occurred in both soma and dendrites of neurons and all types of glial cells. A unique configuration of collapsed agranular cisterns also was observed in aged animals. The present results indicate that decreases in synaptic density may be one morphological event underlying functional alterations observed in caudate neurons in aged cats.

Subcellular localization of cyclic nucleotide phosphodiesterase in the caudate nucleus.

Abstract The subcellular localization of cyclic nucleotide phosphodiesterase activity is described in the caudate nucleus and the neocortex of the cat and rat. Reaction product is visualized postsynaptically at asymmetrical axodendritic synapses by the statu nascendi precipitation of lead phosphate. The effect of varying substrate concentrations and incubation times to localize enzyme activity at cortical and caudate synapses in the two species is discussed. Demonstration of phosphodiesterase activity at postsynaptic sites adds further indirect evidence suggesting a role for cyclic nucleotides in synaptic transmission.