bluuebunny/crossref_metadata_2025 huggingface dataset:
The origin of spinocerebellar pathways. I. The nucleus cervicalis centralis of the cranial cervical spinal cord
Authors: Cummings J. F. , Petras J. M.
Published: December 2004

The origin of spinocerebellar projections from the cranial cervi cal spinal cord was studied in neonatal dogs following cerebellar ablations or the injection of horseradish peroxidase (HRP) into the cerebellum. Cerebellar ablations produced distinct retrograde changes of three types: type I response or cen tral chromatolysis; type II response or ghost cells; and type 111 response or neu ronal loss and gliosis. These ablation‐induced changes were evident in the cells of the nucleus cervicalis centralis. The results of hemicerebellectomy, unilateral cer ebellar pedunculotomy, and cordotomy established that the cells of this nucleus project contralaterally to the cerebellum. Cytoarchitectonic study revealed that this nucleus is composed of clustered medium‐sized, multipolar, chromatophilic neurons located in the zona intermedia of the C1‐C4 segments. The retrograde la beling of central cervical neurons following cerebellar injections of HRP con firmed the results obtained with the axonal reaction.

Anterograde fiber degeneration was present in the central cervical nucleus following dorsal rhizotomy in the dog and cat. These experiments demonstrated dorsal root fibers among the somata of central cervical neurons rendered chromatolytic following cerebellectomy in the dog. Electron microscopic evidence is presented for the presence of degenerated dorsal root terminals upon the dendrites and somata of central cervical neurons.

The nucleus cervicalis centralis forms a direct link between neck afferents and the cerebellum by way of a crossed cervicospinocerebellar pathway. Evidence could not be found for the presence of a spinocerebellar projection originating in the nucleus ceruicalis lateralis.
The distribution of acetylcholinesterase in the central nervous system of jumping spiders and wolf spiders (Arachnida, Araneida: Salticidae et Lycosidae)
Authors: Meyer Wilfried , Idel Karl
Published: December 2004

The distribution and activity pattern of acetylcholinesterase in the central nervous system of salticid and lycosid spiders has been studied. Enzyme activity was limited to the neuropile mass. The salticid and lycosid species investigated showed different intensities of enzyme reactions in the protocerebrum. The differences observed may be related to the some what contrasting habits of these spider families. Reactions were strong especially in the optic ganglia (lamina glomerularis, corpora pedunculata) and in the cerebral ganglion, while the central body showed only weak to moderate activity. In the cheliceral ganglia, as in the pedipalpal and the leg ganglia, including the fibre tracts of the ventral cord the demonstration of acetylcholinesterase was of moderate to strong intensity.
The effect of cortical lesions upon visual discriminations in binocularly deprived cats
Authors: Loop Michael S. , Sherman S. Murray
Published: December 2004

Four cats were raised with binocular eyelid suture and, after their eyes were opened, were trained on a series of discrimination tasks. They performed at normal rates on the brightness task but indicated some difficulty with the pattern tasks. They then received large, bilateral occipito‐temporal cortex ablations. Postoperatively, this in no observable way affected their visually guided orienting behavior, but it did destroy their capacity to perform the preoperatively learned pattern tasks. Postoperative performance on the brightness task remained good. These data indicate that, in these deprived cats, there is little or no cortical development for visual orienting, but cortex is necessary for visual discrimination learning.
Presence of labeled monocytes, macrophages and microglia in a stab wound of the brain following an injection of bone marrow cells labeled with 3H‐uridine into rats
Authors: Imamoto K. , Leblond C. P.
Published: December 2004

To clarify the origin of the cells appearing in a stab wound of the parietal cortex, bone marrow cells from inbred Lewis rats were labeled in vitro with 3H‐uridine and injected intravenously into 36 rats of the same strain Just before or after the brain had been stabbed. The animals were sacrificed from 1 to 15 days after the injection of labeled cells. The cells in the wound were examined and the percentage of the various types recorded. Radioautographs were prepared of the wound and the surrounding neuropil, as well as of the corresponding region on the intact side; and they were searched for labeled cells.

One day after the stabbing, the wound consisted of a central region containing fluid and red blood cells, and a marginal region of disorganized nervous tissue including granulocytes, monocytes and macrophages. Around the wound, the neuropil appeared normal, except for the perivascular areas appearing more cellular and distended than normally.

During the next few days, the granulocytes and monocytes gradually disappeared from the wound. Meanwhile, the macrophages, which initially often showed monocytic features, became increasingly numerous. However, after the seventh day, the macrophages decreased in number, while many small cells appeared in the wound. These displayed a scanty basophilic cytoplasm rich in phagosomes and a nucleus with dense chromatin clumps similar to that seen in microglia

A search of the radioautographs revealed no labeled cell on the intact side, but 220 labeled cells on the injured side. Most of these cells were within the wound itself, and a few in the surrounding neuropil. Within the wound, labeled granulocytes and monocytes were common one day after injection, but disappeared after the first three days. Few labeled macrophages were observed at one day but many at three days; none were labeled after the seventh day, however, possibly due to turnover and loss of the 3H‐uridine labeled RNA.

In the neuropil surrounding the wound, a few labeled cells identified as microglia were observed during the first three days after injection. They were located in perivascular areas, in satellite position to neurons and within the nearby subependymal layer

It is concluded that, under the influence of a stab wound, blood cells of bone marrow origin enter the wound and the surrounding neuropil. The presence of macrophages with monocytic features within the wound indicates that the monocytes transform into macrophages. The small cells displaying phagosomes and a microglia‐like nucleus, which become numerous after the seventh day, are tentatively interpreted as intermediates in the transformation of the monocytederived macrophages into microglia. Finally, the early labeled cells identified as microglia in the surrounding neuropil are interpreted as a direct transformation of monocytes into microglia.
The distribution of 3H‐Leucine labeled protein in the retinula cells of the crayfish retina
Authors: Hafner G. S. , Bok Dean
Published: December 2004

The synthesis and distribution of 3H‐leucine labeled protein was studied under conditions of diurnal lighting in the retinula cells of the crayfish retina with both light and electron microscopic autoradiography. Times ranging from two minutes to seven days after an intracardiac injection were analyzed. Quantification of the electron microscopic autoradiograms revealed that labeling of the cytoplasm was greater than the rhabdome at 2, 5, and 30 minutes and reached a peak at 12 hours. The rhabdome showed increasing activity after 5, 30, and 60 minutes, also reaching a peak at 12 hours. Radioactive label in cytoplasmic multivesicular bodies was higher than activity measured in either the total cytoplasm or rhabdome at all times except two minutes.

Two temporally different microvillar labeling patterns were seen under diurnal lighting conditions. (1) Microvilli forming the slightly enlarged distal tip of the rhabdome retained their radioactivity at 1, 3, and 7 days, when labeling of the rest of the rhabdome microvilli was decreasing. (2) In the remainder of the microvilli, labeling at 1 and 12 hours appeared as a gradient which declined toward the proximal end of the rhabdome. This gradient subsequently reversed itself, showing heavier proximal labeling at three days.

In a second experiment, labeling patterns in light and dark adapted rhabdomes were compared. In the dark, a distinct gradient of activity was observed with radioactivity concentrated distally and declining toward the proximal end of the rhabdome. A more even distribution of label was present in the light adapted eye, but a slight distal‐proximal gradient was still present. The dark adapted rhabdomes had more radioactivity per unit area than those exposed to light.
Postnatal differentiation of cell body volumes of spinal motoneurons innervating slow‐twitch and fast‐twitch muscles
Authors: Sato Manabu , Mizuno Noboru , Konishi Akira
Published: December 2004

Distribution of cell body volumes of motoneurons innervating the soleus (slow‐twitch or tonic) and medial gastrocnemius (fast‐twitch or phasic) muscles was examined in adult cats and a series of kittens ranging from one to 140 days in age. To identify the soleus (Sol) and the medial gastrocnemius (MG) motoneurons, each group of motoneurons was labeled differentially by utilizing retrograde axonal transport of horseradish peroxidase injected into the muscles.

It was verified statistically that in the adult cat, the mean cell body volume of the Sol motoneurons was smaller than that of the MG motoneurons. Difference of the mean cell body volume between the Sol and MG motoneurons was found to be significant around the tenth postnatal day. The mean cell body volumes of both Sol and MG motoneurons increased mainly during the third to the seventh week after birth. After this period, increase of the cell body volume was relatively slight and in the fifth month after birth, some of the motoneurons still appeared to be growing. Our findings also suggested that the MG motoneurons may exhibit the adult pattern of distribution of cell body volume in an earlier postnatal stage than do the Sol motoneurons, and that differentiation of motoneurons into the gamma and alpha types may occur earlier than differentiation into the tonic and phasic types.
Growth of the corticospinal tract and the development of placing reactions in the postnatal rat
Authors: Donatelle Janet Marie
Published: December 2004

The growth of corticospinal axons into the spinal cord has been demonstrated using the autoradiographic and the Fink‐Heimer silver degeneration methods. In addition, the development of several types of placing reactions has been studied. After unilateral injections of radioactive proline or unilateral injections of radioactive proline or unilateral ablations of the somatosesory‐motor cortex, corticospinal axons were found to extend into the contralateral dorsal funiculus of the lower cervical cord at one day postnatally, into mid‐thoracic segments at three days, into upper lumbar cord by five days and into coccygeal segments by nine days. Corticospinal axons are first present in the contralateral spinal gray of lower cervical cord at day 5 and in the contralateral spinal gray of lower lumbar and sacral cord by day 9. Little change in the topographical distribution or in the density of the projection is found at all levels of the spinal gray after the fourteenth postnatal day. Comparable results were found with both experimental techniques.

Forelimb placing is first seen between 4 to 7 days and hind limb placing between 9 to 13 days. The last placing response to appear in both the forelimbs and the hindlimbs is placing in response to tactile and light proprioceptive stimuli. After the initial onset of the placing reactions, there is a gradual increase in the frequency and speed of the responses until 14 to 17 days postnatally, at which time the reactions appear to be mature.

While a causative relationship between the growth of corticospinal axons into the spinal cord and the development of placing has not been established, a close temporal relationship has been found between first: the appearance of fore‐ or hindlimb placing responses and the appearance of corticospinal axons within the spinal gray at the appropriate levels of the cord and second: between the completion of the primary growth of corticospinal axons at the light microscopic level and the maturation of the placing reactions.
Anatomical and neurobehavioral investigations concerning the thalamo‐cortical organization of the rat's visual system
Authors: Hughes Howard C.
Published: December 2004

The organization of thalamic afferents to the rat's visual cortex was investigated autoradiographically and through the retrograde transport of horseradish peroxidase (HRP) following injections into striate and peristriate cortex. The results revealed that Nucleus lateralis posterior (NLP) projects to a large peristriate cortical field that includes areas 18A, 7, and the anterior portion of area 18, and to a circumscribed temporal area corresponding to Krieg's ('46a,b) area 20. The dorsal lateral geniculate nucleus (LGNd) was shown to project to two spatially discontinuous cortical areas. The largest geniculate receiving area is partially coextensive with Krieg's area 17, but an extension of this projection posterior and medial to the striate cortex was found. In addition, a geniculate projection to a restricted field located in the lateral peristriate cortex was identified.

Concurrent investigations were designed to assess the pattern discrimination abilities of rats prepared with striate cortical ablations, lesions in NLP and combined striate‐cortical and thalamic ablations. Comparison of these animals with normal control subjects revealed that the striate cortex in the rat (as in the cat [Doty, '71; Sprague et al., '77] and the tree shrew [Killackey and Diamond, '71; Ware et al., '74]) is not necessary for successful pattern discrimination, and that the geniculo‐striate and NLP‐extra‐striate projection systems are both involved in mediating the visual discriminative abilities of the rat.

The results add species generality to the concept that the central connections to the visual cortex are characterized by parallel‐conducting thalamic channels and contribute to the growing number of demonstrations that the extra‐striate cortex and associated thalamic cell groups contribute significantly to the process of visual‐pattern recognition.
The nucleus corporis pontobulbaris of the North American opossum
Authors: Martin G. F. , Linauts M. , Walker J. M.
Published: December 2004

The nucleus of the pontobulbar body (PBu) in the North American opossum is located, for the most part, adjacent to the motor root of the trigeminal nerve. Material prepared by degeneration and autoradiographic methods shows that the PBu receives projections from the facial motor‐sensory cortex, red nucleus, spinal cord and cerebellum. The latter fibers probably take origin within the fastigial nucleus. Each of the afferent connections ends in a restricted part of the PBu, but there is considerable overlap. Use of the horseradish peroxidase technique reveals that the PBu projects to the spinal cerebellum (anterior lobe, pyramis and paramedian lobules), to visual‐auditory areas of the vermis and to the lobus simplex as well as to crus I and II of the hemispheres. Although there is some topography to such projections, it is not sharply defined and many regions of the PBu contain labelled neurons after injections of horseradish peroxidase into widely separate areas of the cerebellar cortex.

Because of its embryogenesis and position, the PBu is often considered part of the dorsolateral basilar pons. It appears from our material, however, that the organization of PBu afferent and efferent connections is different from that of the adjacent basilar pons, and arguments for considering the PBu a separate precerebellar nucleus are presented.
Size, laminar and columnar distribution of efferent cells in the sensory‐motor cortex of monkeys
Authors: Jones E. G. , Wise S. P.
Published: December 2004

The cells of origin of cortico‐cortical and subcortical projections from the subfields of the somatic sensory area and from the motor cortex have been identified in cynomolgus and squirrel monkeys by the retrograde axonal transport method.

The somata of the cells of origin of a particular fiber system have a specific laminar or sublaminar distribution. The somata of the majority of cortico‐cortical cells lie in the supragranular layers. Those projecting to the opposite cortex are confined to the deeper half of layer III (layer IIIB). Ipsilateral cortico‐cortical neurons lie mainly superficial to them in layers IIIA and II, but in the second somatic sensory area (SII) and in area 2 of the first (SI), small numbers are also found in layer V. Corticospinal cells lie in the deeper part of layer V and corticostriatal cells in the superficial part. Corticopontine, corticobulbar and corticorubral cells lie in between. The majority of corticothalamic cells lies in layer VI but a second, smaller population is found in the deep part of layer V.

The cells giving rise to a particular set of efferent connections can be distinguished in terms of size and, with the exception of the corticospinal cells, their size does not vary greatly from area to area. In many cases, the size and laminar specificity indicates that cells sending axons to one site cannot have collateral branches projecting to another.

In most of the fiber systems studied, labeled cells form single or multiple strips, 0.5–1 mm wide and oriented mediolaterally across the cortex. The strips appear in all of the subfields of the somatic sensory and motor areas and may form the basis of the clustering of like groups of efferent neurons demonstrable in physiological studies.
Topographic projections between the nucleus isthmi and the tectum of the frog rana pipiens
Authors: Gruberg Edward R. , Udin Susan B.
Published: December 2004

The connections between the nucleus isthmi and the tectum in the frog have been determined by several anatomical techniques: iontophoresis of horseradish peroxidase into the tectum, iontophoresis of 3H‐proline into the nucleus isthmi and the tectum, and Fink‐Heimer degeneration staining after lesions of the nucleus isthmi. The results show that the nucleus isthmi projects bilaterally to the tectal lobes. The ipsilateral isthmio‐tectal fibers are distributed in the superficial layers of the tectum, coincident with the retinotectal terminals. The contralateral isthmio‐tectal fibers travel anteriorly adjacent to the lateral optic tract and cross the midline in the supraoptic ventral decussation, where they turn dorsally and caudally; upon reaching the tectum, the fibers end in two discrete layers, layers 8 and A of Potter. The tectum projects to the ipsilateral nucleus isthmi and there is a reciprocal topographic relationship between the two structures. Thus, a retino‐tecto‐isthmio‐tectal route exists which may contribute to the indirect ipsilateral retinotectal projection which is observed electrophysiologically. The connections between the nucleus isthmi and the tectum in the frog are strikingly similar to the connections between the parabigeminal nucleus and the superior colliculus of mammals.
Retinal ganglion cells in the crucian carp (Carassius carassius). I. Size and number of somata in eyes of different size
Authors: Kock Jan‐Henrik , Reuter Tom
Published: December 2004

Ganglion cell somata were drawn, measured and counted in flatmounted crucian carp and goldfish retinas stained with cresyl violet or methylene blue. Soma diameter histograms suggest that the ganglion cells can be divided into two populations with overlapping soma sizes: a large group of small cells and a small group of large cells, the latter constituting 2.5–5% of all ganglion cells. With increasing distance from the optic disc the mean soma diameter increases while the ganglion cell density decreases. In a peripheral growth zone close to the margin the ganglion cells become smaller again.

The total number of ganglion cells in retinas of different size was calculated from the areas of the flat‐mounted preparations and the cell densities in two representative regions. In the crucian carp population used in this work the total number of ganglion cells per retina was found to increase from roughly 140,000 (mean of 8 scattered values) to a full 200,000 between eye diameters 4 and 10 mm, this increase taking place mainly between eye diameters of 4 and 6.5 mm.

Thus, due to a drastically decreasing cell density, the total number of ganglion cells increases only by a factor of about 1.5 while the retinal area becomes sixfold. During the same growth period the mean soma diameter increases by a factor of about 1.3 and the soma volume more than doubles. The optic nerve of a small crucian carp was studied by electron microscopy. About equal numbers of unmyelinated and myelinated axons were found. The axons in the optic nerve are, on an average, considerably thicker than the axons on the retinal surface.
Embryonic behavior, hatching and neuromuscular development in the chick following a transient reduction of spontaneous motility and sensory input by neuromuscular blocking agents
Authors: Oppenheim Ronald W. , Pittman Randall , Gray Marjory , Maderdrut Jerome L.
Published: December 2004

Embryos were immobilized with neuromuscular blocking agents for one to four days between days 10 and 15 of incubation. This treatment reduces spontaneous motility, as well as movement‐initiated proprioceptive and cutaneous stimulation. Although the major aim of these experiments was to determine the effects of such treatment on subsequent behavioral development, several indices of neuromuscular and general morphological development were also examined.

A single injection of curare on day 10 continues to depress spontaneous motility for virtually the entire remaining incubation period. This effect is due to the persistence of unmetabolized curare in the closed system of the egg. When a comparable dose of a rapidly metabolized neuromuscular blocking agent (succinylcholine) is given, this long term behavioral depression is not found. Embryos treated with SC can remain totally immobilized for up to 60 hours with no apparent repercussions on subsequent behavior; spontaneous embryonic motility, reflex sensitivity, hatching, and several general posthatching behaviors, all appeared normal following such treatment.

Embryos immobilized for as little as 48 hours developed joint malformations and were retarded in general growth by about one day whereas 24 hours of paralysis was not sufficient to induce these effects.

Twenty‐four hours of total paralysis from days 10 to 11, plus a 40–50% reduction in motility until days 15 or 16, does not appear to cause any abnormalities in muscle or spinal cord development. Muscle histology, motor endplates, cell number in the spinal cord and choline acetyltransferase and acetylcholinesterase activity in spinal cord and muscle were all comparable to controls. An 80–90% reduction in motility on days 11 through 15, however, induces an apparent alteration of the intensity and distribution of histochemically demonstrable AChE in the anterior and posterior latissimus dorsi muscles.

The present findings suggest that the suppression of overt motility for a period comprising ca. 5–12% of the total incubation time (21 days) does not modify subsequent behavioral development or the underlying neurogenetic mechanisms. Though these findings provide some support for the notion that the embryonic nervous system develops in forward reference to and without benefit from function or sensory input, only a more complete reduction of neural function, especially CNS activity, can provide a critical test of this concept.
The developmental morphology of Torpedo marmorata: Electric organ — Myogenic phase
Authors: Fox Geoffrey Q. , Richardson Guy P.
Published: December 2004

The early development of the electric organ of Torpedo marmorata has been examined by light and electron microscopy to the 40‐mm stage of embryo growth. The myogenic nature of this tissue is confirmed ultrastructurally by the presence of myoblasts and myotubes both containing myofibrils cross striated with Z, A and I bands. Fusion between these cells is also found taking place. A scheme is presented to explain the development of the overall structural plan of the organ and specifically the formation of the future electrocyte columns.

At 40 mm, a series of morphological transformations signals the onset of a divergent developmental pattern ultimately leading to the establishment of mature electrocyte columns. These features include rounding up of myotubes, dissolution of myofibrils and the appearance of intermediate size filaments (11 nm) and perhaps a non‐muscular actin (5.5 nm). This early myogenic phase of development occurs in the absence of any specific nervous contact even though electromotor nerves are always in close proximity.
Photoreceptors and oil droplet colors in the red area of the pigeon retina
Authors: Mariani Andrew P. , Leure‐Dupree Alphonse E.
Published: December 2004

Six types of photoreceptors in the red area (dorso‐temporal quadrant) of the pigeon retina are identified using Golgi impregnation, light microscopy and electron microscopy. Golgi impregnation is used to categorize the receptors into morphological types. Examination of oil droplets in the inner segments of cones in fresh, unfixed tissue shows five different types which can be characterized by color, size and stratification. Therefore, in sections through the length of the receptors examined by electron microscopy, the oil droplets contained in the inner segments of the cones can be identified as to their color by their characteristics (i.e., size and stratification), and the groups of receptors thus classified, further characterized as to the morphology of their terminals. Rods have no oil droplets in their inner segments, and their synaptic terminals are located in the outermost stratum of the outer plexiform layer (OPL). Principal members of double cones have yellow oil droplets in their inner segments, while accessory members contain small colorless oil droplets. The synaptic terminals of double cones are located in the same (outermost) stratum of the OPL as rod synaptic terminals. Two types of single, straight cones house either red or orange oil droplets and terminate in the intermediate stratum of the OPL. Oblique single cones with yellow‐green oil droplets in their inner segments contribute synaptic terminals to the innermost stratum of the OPL.
A golgi study of cell types in the hilar region of the hippocampus in the rat
Authors: Amaral David G.
Published: December 2004

The morphology of neurons in the “hilar region” of the hippocampus (fields CA3c and CA4 of Lorente de Nó, '34) was analyzed with several variants of the Golgi technique. Hippocampi were dissected from the brains of 28‐day‐old rats, fixed and impregnated by immersion, and sectioned perpendicular to the long axis. Based on the resident cell types, aspects of the neuropil, and published data related to afferent termination, the area under study was divided into four zones. At least 21 cell types were observed throughout these zones, several of which had not previously been described. Many cells in this area exhibited an impressive number and variety of dendritic and axonal appendages, including spines on the proximal portion of some axons. The close apposition of fibers to these axonal spines suggested the possibility of axo‐axonal interactions. The influence of dentate granule cells, through their mossy fibers, on the synaptic economy of the “hilar region” was found to be more extensive than previously reported. Mossy fibers appeared to terminate on the dendrites of several types of non‐pyramidal cells, which bear no thorny excrescences, by means of thin filiform extensions which emanate from the mossy fiber expansions and by means of thin mossy fiber collaterals which are devoid of typical expansions. Consideration is given to a long‐standing debate as to whether the deep “hilar region” (CA4 of Lorente de Nó, '34, hilus of the fascia dentata of Blackstad, '56) is related more to the hippocampus or to the fascia dentata and it is concluded that the deep hilar region is an area of mergence of the polymorphic zones of these two cortical structures. The results of the present study do not support the proposition that the deep hilar region is an extension of the pyramidal layer of the hippocampus as suggested by Lorente de Nó ('34), and thus CA4 is a misnomer. Rather, the cells in this area are most closely related to the fascia dentata and should thus be considered to lie in the polymorphic zone of “area dentata” as proposed initially by Blackstad ('56).
The morphology of the hippocampus and dentate gyrus in normal and reeler mice
Authors: Stanfield Brent B. , Cowan W. Maxwell
Published: December 2004

The morphology of the hippocampus and dentate gyrus in normal and reeler mice has been studied in Nissl, myelin, Golgi, Timm's sulfide silver and gold chloride‐sublimate preparations. It is evident form both cell‐and fiber‐stained sections that despite the obvious defect in the positioning of the hippocampal pyramidal and dentate granule cells in the reeler mouse with in the radial dimension, the hippocampal formation as a whole shows a normal and consistent progression of cytoarchitectonic fields along its transverse axis, and a normal and consistent progression of changes in the structure of the hippocampus and dentate gyrus along their longitudinal axes. Thus, at least in these structures, the reeler gene seems to exert its effect only in the radial dimension.

Cell counts in the area dentata indicate that the number of dentate granule cells in the reeler mouse is reduced compared to that found in normal or heterozygous animals. Although it has been known for some time that the number of granule cells in the reeler cerebellar cortex is markedly reduced, this appears to be the first evidence of a reduction in cell number in a forebrain structure.

All the major cell types normally found in the hippocampus and the dentate gyrus are recognizable in Golgi‐stained preparations from the brains of reeler mutants. However, in both regions there are a number of abnormalities in the appearance of the cells which seem to be related to the cellular ectopia. Thus, whereas most of the pyramidal and granule cells which attain a normal position in the mutant usually have normal, or near‐normal dendritic arbors, the dendrites of nearly all ectopic cells are severely distorted, both in their orientation and general configuration. In preparations stained by the Timm's sulfide silver technique it is evident that the general lamination pattern seen in normal mice is retained in the reeler hippocampus and dentate gyrus despite the gross malpositioning of many of the relevant neurons. However, although the overall laminar arrangement is preserved, there are some fairly consistent abnormalities; for example, the normal trilaminar staining pattern seen in the stratum moleculare of the dentate gyrus is replaced in the reeler by a bilaminar pattern.

In gold chloride‐sublimate impregnated preparations there is no obvious alignment of the astrocytes in the stratum moleculare of the dentate gyrus in either normal or reeler mice. Moreover, the distribution of the astrocytes with in this zone is fairly normal in the reeler mouse, although, in general, these cells appear to be more consistently stellate in form than in normal animals.
The organization of certain afferents to the hippocampus and dentate gyrus in normal and reeler mice
Authors: Stanfield Brent B. , Caviness Verne S. , Cowan W. Maxwell
Published: December 2004

The organization of certain of the major afferents to the hippocampus and dentate gyrus has been studied in normal and reeler mutant mice using the autoradiographic and the anterograde degeneration methods. The distribution of the hippocampal and dentate afferents which arise in the medial and lateral parts of the entorhinal cortex and the hippocampus of both sides, has been found to be generally similar to that previously described in the rat, but there are a few minor differences that are discussed in the text.

Despite the marked ectopia of many of the neurons in the hippocampal for mation in the reeler mouse, the Principal afferents to the hippocampus and the dentate gyrus maintain many of the features seen in normal mice. In particular, they maintain a normal radial sequence and a characteristic laminated and complementary arrangement. However, there are a number of significant differences in their distribution; for example in the reeler mouse, the entorhinal afferents occupy the entire extent of the stratum moleculare of the dentate gyrus, whereas in normal mice they are restricted to the outer four‐fifths of this layer. Furthermore, in the mutant the commissural and associational afferents to the dentate gyrus do not occupy the inner one‐fifth of the molecular layer (as they do in normal animals) but rather are spread throughout the zone containing granule cells, which includes both the poorly‐defined stratum granulosum and most of the hilar region of the dentate gyrus. Some of the developmental and functional implications of these and other abnormalities in the organization of the afferents to the hippocampus and dentate gyrus are discussed.
The effects of eliminating impulse activity on the development of the retinotectal projection in salamanders
Authors: Harris William A.
Published: December 2004

The California newt Taricha torosa manufactures tetrodotoxin, a blocker of voltage‐sensitive sodium channels and therefore of action potentials. The newt's own nervous system is insensitive to this toxin. Grafting an embryonic eye to the newt from a tetrodotoxin‐sensitive species, the Mexican axolotl, blocks action potentials in the retinal ganglion cells of the transplanted eye. Neuroanatomical and electrophysical techniques demonstrate that while such ganglion cells are incapable of firing impulses, they develop normally, grow axons to the host tectum, terminate in the appropriate neuropil layers, form synapses, and project to the tectum retinotopically. Furthermore, they develop these apparently normal projections even in competition with electrically active axons from a host eye.
The distribution of cholecystokinin‐like immunoreactive neurons and nerve terminals in the retrohippocampal region in the rat and guinea pig
Authors: Köhler Christer , Chan‐Palay Victoria
Published: December 2004

The distribution of cholecystokinin (CCK)‐like (CCK‐L) immunoreactive cells and nerve terminals was studied in the brains from rats and guinea pigs by using antibodies to the octapeptide cholecystokinin (CCK‐8). Analysis of serial horizontal and sagittal sections through the retrohippocampal region in colcicine‐pretreated rats revealed a relatively large number of CCK‐L immunoreactive cells in the pre‐ and parasubiculum, subiculum, and the medial and lateral entorhinal area (EA) at all dorsal to ventral levels of the region. In the EA, the CCK‐positive cells were scattered in all layers without any clear pattern. Analysis of CCK‐positive cells in the retrohippocampal region showed that these cells form a morphologically heterogeneous group. The types of CCK‐L immunoreactive cells ranged from small(∼10 μm) round, ovoid, or fusiform to large (∼30μm) multipolar and pyramidal. CCK‐L immunoreactive nerve fibers and preterminal processes were unevenly distributed in the retrohippocampal region. The densest innervation was found in the parasubiculum, subiculum, and the ventrolateral entorhinal area. Only a few scattered fibers were detected in the molecular layer of these structures and the outer layers of the presubiculum. Within the EA the CCK innervation indicated a heterogeneous laminar distribution that was densest in layers II and IV of the medial and lateral EA and diffuse in layers I and III. In layer II the immunoreactive nerve terminals encircled the payramidal cell bodies, while in layers IV to VI and the most ventral part of lateral entorhinal area (LEA) and the transitional area between LEA and piriform cortex the CCK processes were distributed in a netlike fashion without clear relation to the cytoarchitectural characteristics of the area.
The medial accessory nucleus of bechterew: A cell group within the anatomical limits of the rostral oculomotor complex receives a direct prefrontal projection in the monkey
Authors: Leichnetz George R.
Published: December 2004

The medial accessory nucleus of Bechterew, a vertically oriented cell group in the rostral lateral oculomotor nucleus (OMN), contiguous dorsally with the nucleus of DarKschewitsch (ND) and ventrally with the parvocellular red nucleus, is separated from the interstitial nucleus of Cajal (IC) by a small paraoculomotor fascicle (POF) that forms the anatomical limits of the OMN. Horseradish peroxidase (HRP) gel implants in the prearcuate frontal cortex dorsal to the caudal third of the principal sulcus in the monkey resulted in an anterogradely labeled bilateral projection to this paraoculomotor cell group. The functional role of this largely overlooked nucleus is yet to be determined. However, the failure to retrogradely label following HRP injections involving both the extraocular muscles and ciliary ganglion suggests that it cannot be classified as belonging to either the somatic or the visceral cell column at the present time. We suggest that, like IC and ND, it probably contributes to the POF of the medial longitudinal fasciculus and may be involved in internuclear connections. There is little doubt that it has been involved inadvertently in studies of oculomotor connections.
Brainstem afferents to the thalamus in a lizard, Varanus exanthematicus
Authors: Hoogland Piet V.
Published: December 2004

HRP was injected into various thalamic nuclei in order to investigate the brainstem projections to the thalamus in the lizard Varanus exanthematicus. Nucleus dorsomedialis receives afferents from the septal area, nucleus entopeduncularis anterior, nucleus periventricularis hypothalami, area triangularis, nucleus raphes superior, nucleus reticularis inferior, and locus coeruleus. Nucleus dorsolateralis receives afferents from septal area, nucleus dorsomedialis, nucleus entopeduncularis anterior, nucleus periventricularis hypothalami, and the torus semicircularis. Nucleus rotundus receives an input from the tectum mesencephali, the pretectal area, and from the mesencephalic reticular fromation. Nucleus intermedius dorsalis receives afferents from the dorsal column nuclei and nucleus periventricularis hypothalami. Nucleus ventrolateralis receives afferents from the dorsal column nuclei, the trigeminal complex, locus coeruleus, and the reticular formation. Nucleus ventromedialis also receives afferents from the trigeminal complex and the reticular formation. Afferents to the habenula have been demonstrated from the septal area, nucleus entopeduncularies anterior triangular area, nucleus periventricularis hypothalami, nucleus interpeduncularis, nucleus raphes superior, locus coeruleus, nucleus isthmi, nucleus dorsalis motorius nervi vagi, and the mesenscephalic tegmentum. The laminar part of the torus semicircularis projects to nucleus medialis.
Afferent neurons in the hypoglossal nerve of the zebra finch (Poephila guttata): Localization with horseradish peroxidase
Authors: Bottjer Sarah W. , Arnold Arthur P.
Published: December 2004

Hypoglossal efferent fibers are known to innervate the vocal organ (syrinx) in songbirds. In order to determine the existence of afferent fibers from the syrinx in the zebra finch, horseradish peroxidase (HRP) was applied to the cut peripheral branch of the hypoglossal nerve that innervates the left side of the syrinx. Cell bodies in the ganglion of the left vagus nerve were labeled, but no transganglionic (anterograde) transport into the CNS was observed at transport intervals of 1 to 5 days. (In comparision, applying HRP to the cut descending branch of the vagus produced labeled cell bodies in the vagal ganglion as well as heavy anterograde label extending into the solitary nucleus.) Injection of HRP conjugated to wheat germ agglutinin into the intrinsic syringeal muscles also labeled cell bodies in the vagal ganglion, and again no transganglionic label was observed. Application of HRP more proximally to the cut hypoglossal trunk resulted in the appearance of labeled cell bodies in the vagal ganglion as well as anterograde label extending from the decending trigeminal tract to the principal sensory nucleus of V. These results indicate that hypoglossal afferents have cell bodies in the vagal ganglion, enter the medulla dorsally with vagal fibers, and terminate in the trigeminal complex. The identification of these afferent fibers raises the important question of their role in vocal learning.
A laminar analysis of the number of neurons, glia, and synapses in the visual cortex (area 17) of adult macaque monkeys
Authors: O'Kusky John , Colonnier Marc
Published: December 2004

The number of neurons, glia, and synapses in the visual cortex of adult macaque monkeys has been estimated by stereological methods. The data is presented separately for 13 sublaminae. For the total cortical thickness, the average numerical density of neurons is approxiametly 120,000 per mm3 of tissue. This density increases and decreases in the different sublaminae in the direction that one would expect from the classical descriptions of Nissl‐stained material (e.g., 137,000/mm3 in IVCα; 211,000/mm3 in IVCβ). There are about 200,000 neurons under 1 mm2 of cortical surface: 28% are in layers I‐III, 45% are in layer IV, and 27% are in layers V and VI. The total number in area 17 of one hemisphere is close to 160,000,000. For the total cortical thickness the numerical density of synapses is 276,000,000 per mm3 of tissue. Laminae with higher neuronal densities tend to have higher synaptic densities but the correlation is not perfectly concordant. Moreover, the changes in synaptic densities are not as great as those in neurol densities so that laminae with higher neuronal densities have a lower synapse to neuron ratio and laminae with lower neuronal densities have a higher synapse to neuron ratio. For the total cortical thickness this ratio is 2,300 synapses per neuron (1,400 in layer IVCβ and 2,800 in layers II and III). There are 478 million synapses under 1 mm2 of cortical surface: 40% are in layers I–III, 35% are in layer IV, and 25% are in layers V and VI. The numerical densities of astrocytes, oligodendrocytes, and microcytes are 38,000, 17,000, and 4,000 per mm3, respectively. The overall glia/neuron ratio is 0.49.
Postnatal changes in the number of neurons and synapses in the visual cortex (area 17) of the macaque monkey: A stereological analysis in normal and monocularly deprived animals
Authors: O'Kusky John , Colonnier Marc
Published: December 2004

The surface area of the striate cortex and the thickness of its laminae were measured in a series of newborn, 3‐month, 6‐month, and adult macaque monkeys. The numerical densities (Nv) of neurons and synapses were measured in individual laminae. The total numbers of neurons and synapses in the striate cortex of one hemisphere were derived from these measures. Normal monkeys were compared at 3 months and 6 months of age to animals having been reared from birth with a monocular eyelid suture. No significant differences were observed between normal and monocularly deprived monkeys. The perceptual deficits and physiological abnormalities that have been reported in monocularly deprived monkeys do not appear to result from a reduction in the amount of neural circuitry in the striate cortex. The combined data from these groups, however, demonstrated several developmental changes. Cortical thickness increased from birth to 6 months and diminished to near‐newborn values in the adult. The 6‐month cortex was 19% thicker than that of adult. This overshoot was greatest in layers II and III, which were 43% thicker at 6 months. Cortical surface area demonstrated a similar trend, being 23% greater at 6 months, but the differences were not statistically significant. The Nv of neurons decreased from birth to 6 months and increased to near‐newborn values in the adult. The 6‐month Nv was 30% less than that of adults and the greatest changes were seen in layers II and III where the Nv was 38% less than adult values. The total number of neurons in the striate cortex of one hemisphere was 16% less in adults than in newborn animals, but statistically significant neuron losses were limited to layers I, II, IVCα, V, and VI. The Nv of synapses increased from birth to 6 months and diminished to near‐newborn values in the adult. The 6‐month overshoot was 34% for the total cortex and 41% for layers I–III. The total numbers of synapses in the striate cortex was 95% greater at 6 months than in the adult. In layers I–III the synapses were 130–155% more numerous at 6 months. These data demonstrate an increase in neuronal connectivity in the striate cortex from birth to 6 months, especially in layers I–III, and a subsequent decrease in the adult.
The fine structure of the perigeniculate nucleus in the cat
Authors: Ide Linda S.
Published: December 2004

The fine structure of the cat's perigeniculate nucleus has been analyzed and compared to that of dorsal thalamic relay nuclei. Golgi preparations and electron micrographs of perigeniculate cells commonly show somatic spines. The most common presynaptic elements for these spines and for the adjacent perikaryal surfaces are relatively large axon terminals containing round synaptic vesicles and making multiple asymmetric contacts. These “RLD” terminals (so termed for their round vesicles, large average size of the terminals, and dark mitochondria) are also presynaptic to dendritic spines and shafts of proximal and secondary dendrites. Comparisons with adjacent parts of the dorsal lateral geniculate nucleus show that these RLD terminals are cytologically distinct from retinogeniculate terminals and that small numbers of RLD terminals also occur in the geniculate A laminae. Three other major classes of perigeniculate synaptic terminals, resemble major classes of terminals in the dorsal lateral geniculate nucleus. These include two types of terminal with flat or ovoid synaptic vesicles and dark mitochondria, “FD1” and “FD2” terminals, and a class of small terminal with densely clustered round vesicles and dark mitochondria, “RSD” terminals. RSD terminals, which resemble corticogeniculate axon terminals, represent the only class of perigeniculate terminal that does not contact perikarya. FD2 terminals resemble lateral geniculate presynaptic dendrites and participate in serial and triadic synaptic contacts, being both pre‐ and postsynaptic; however, in contrast to the arrangement characteristic of thalamic relay nuclei, these contacts do not occur within synaptic glomeruli. A fifth major class of perigeniculate presynaptic terminal has large flat or polymorphic synaptic vesicles and pale mitochondria. These “FP” terminals are seen infrequently in the lateral geniculate A laminae. Similarities between perigeniculate and lateral geniculate fine structure may relate in part to common sources of afferent input to the two nuclei.