bluuebunny/crossref_metadata_2025 huggingface dataset:
The topographical organization of the hippocampal projection to the septal area: A comparative neuroanatomical analysis in the gerbil, rat, rabbit, and cat
Authors: Siegel Allan , Edinger Henry , Ohgami Shoichiro
Published: January 2005

An experiment was performed to determine the origin of the projection from the hippocampus to the septal area in the subrimate mammalian nervous system. Lesions were made by aspiration or by radio frequency in 4 gerbils, 17 rats, 8 rabbits, and 7 cats. Survival times varied from 2–5 days. Tissues were stained principally with the Fink Heimer I method for identification of degenerating axons and their terminals. Following lesions destroying any one or more of the fields of the dorsal hippocampus of the gerbil, rat, rabbit, or cat, terminal degeneration was observed only in the medial septal area, olfactory tubercle, and adjacent portions of the diagonal band. In addition, lesions producing total destruction of all dorsal hippocampal fields also resulted in the presence of terminal degeneration restricted to the medial septal area. In contrast, superficial lesions of field CA1 of the ventral hippocampus produced terminal degeneration in the lateral septal area, nucleus accumbens, olfactory tubercle, and adjacent portions of the diagonal band. Similar findings were also observed following more widespread lesions of the ventral hippocampus which produced damage to other CA fields as well. Superficial lesions of the posterior crus of the hippocampus (i.e., a position midway between dorsal and ventral hippocampus) resulted in terminal degeneration localized to an intermediolateral region of the septum. Combined lesions of the dorsal hippocampus and fimbria produced widespread terminal degeneration in both the lateral and medial septum indicating that the axons contained within the fimbria arise only from the ventral hippocampus. Finally, lesions of the medial and lateral segments of the fornix of the cat produced terminal degeneration in the medial and lateral regions of the septum, respectively. These findings, collectively, indicate that the origin of the topographical projection to the medial and lateral septum are the dorsal and ventral hippocampus, respectively. This projection is unrelated to cytoarchitectonic fields within the hippocampus and is also invariant among the species considered in this study.
Some histochemical observations on the telencephalon of the bullfrog, Rana catesbeiana shaw
Authors: Northcutt R. Glenn
Published: January 2005

The histochemically determined distribution of acetylcholinesterase, monoamine oxidase and succinate dehydrogenase in the telencephalon of the bullfrog supports the classically recognized divisions of the pallium and subpallium. Analysis also corroborates the following gernerally recognized anuran‐amniotic homologies: anuran medial pallium to amniotic medial cortex anuran septal nuclei to amniotic septal nuclei, anuran striatum to amniotic corpus striatum. On topographical and histochemical criteria the ventrocaudal and basomedial portions of the anuran telencephalon are considered possible homologues to the mammalian amygdala. It is suggested that two divisions can be recognized: a pars lateralis which may be homologous to the mammalian cortico‐medial group. And a pars medialis which may be homologous to the mammalian baso‐lateral group. Further analysis suggests, particularly when viewed in the light of recent experimental anatomical studies, that the anuran lateral pallium consists of a pars dorsalis and a pars ventralis. The pars dorsalis may be the reptilian homologue of the dorsal cortex and the pars ventralis may be the field homologue of both the reptilian piriform cortex and the dorsal ventricular ridge.
Mechanosensory projections to cerebral cortex of sheep
Authors: Johnson John Irwin , Rubel Edwin W. , Hatton Glenn Irwin
Published: January 2005

This study mapped the mechanosensory projections to cerebral cortex of sheep, to complete earlier partial maps and to relate cortical projections to the organization previously determined in ventrobasal thalamus. Tungsten microelectrodes were used to explore thoroughly the walls and depths of cortical sulci as well as the previously studied gyral crowns, for regions responsive to mechanical stimulation of peripheral receptors, in sheep anesthetized with Dialurethane or nitrous oxide with either halothane or methoxyflurane. Earlier findings of a large projection from the ipsilateral mouth, lips and nose were confirmed. In addition, a small representation of the contralateral body and limbs was found which corresponds in most respects to the “second” sensory area (SII) of other mammals. In the primary (SI) sensory cortex, representations of the body and limbs were not found despite thorough fine‐grain mapping. Responses possibly representing a vestige of primary sensory cortex, and mechanosensory responses in claustro‐cortex, were also observed.
The structure and connections of the developing inferior olivary nucleus of the rhesus monkey (Macaca mulatta)
Authors: Robertson Lee T. , Stotler William A.
Published: January 2005

Structural and morphological changes were examined in the inferior olivary complex of 25 rhesus monkeys that were 60 days gestation to three months after parturition. At different ages, one‐half brain stem was sectioned sagittaly, and when possible the symmetrical half was sectioned in either the coronal or the horizontal plane. Serial sections were stained by the silver reduction method of Stotler ('51).

The olivary complex undergoes its major development between 60 and 129 days gestation when its length, cellular morphology, and afferent patterns resemble those of the adult organ. Structurally, the three major divisions—the principal nucleus, the dorsal accessory nucleus, and the medial accessory nucleus—can be identified at 60 days gestation. At that time, the medial accessory nucleus, the largest of the three, can be subdivided into a ventrolateral and a dorsomedial section; as it develops, it extends caudally and acquires a small cap of cells on its dorsomedial part. By 80 days, the dorsal lamella of the principal nucleus, initially smaller than the ventral, equals the ventral lamella in size and continues to enlarge until by 100 days it has developed two large sulci. The dorsal accessory nucleus, the smallest of the three divisions, initially has a distinct connection with the caudal part of the dorsal lamella of the principal nucleus but it is lost by 92 days.

Major afferents to the inferior olive could easily be identified in the early fetal tissue—before the development of the dense neuropil. Afferents first arise from the lateral funiculus of the spinal cord at 60 days and project primarily onto the ventrolateral part of the medial accessory. As they develop, they gradually project more rostrally along the ventrolateral section, onto the dorsomedial section of the medial accessory, onto the caudal part of the ventral lamella, and along the caudomedial part of the dorsal accessory. At 92 days gestation the central tegmental fasciculus, most of which originates from the red nucleus projects into the rostral and later into the middle section of the dorsal lamella, into the rostral ventral lamella, and a few into the rostrolateral part of the dorsal accessory and to the rostral third of the medial accessory. A few fibers arising from the corticospinal tract enter the caudal section of medial accessory, and a few fibers project vertically from the dorsomedial tegmental region of the medulla into the medial section of the dorsal accessory.
Neurons of the dorsal lateral geniculate nucleus of the albino rat
Authors: Kriebel R. M.
Published: January 2005

Light and electron microscopic observations were made on the dorsal lateral geniculate nucleus (DLGN) of 33 young adult male albino rats. Three variants of the Golgi silver impregnation technique were employed in the light microscopic studies.

Neurons were classified into three categories based on location, dendritic pattern, and dendritic appendages. Type 1 and type 3 neurons were distributed throughout the DLGN. Type 2 neurons were located in the superficial zone. Dendritic appendages of type 1 and type 2 neurons indicated these cells may function as geniculocortical relay neurons. The type 3 neurons had lobulated dendritic appendages and an axon that terminated within the nucleus. Type 3 neurons may represent Golgi‐type II interneurons. Camera lucida drawings, photomicrographs, and electronmicrographs illustrate the characteristics of the three cell types. The literature on ultrastructural and neurophysiological findings may substantiate the presence of three neuronal types. Initially, the rat DLGN does not appear as elaborately organized as the nucleus observed in cats and primates; however, there are notable similarities in neuronal morphology and synaptology.
A stereotaxic atlas and technique for forebrain nuclei of the killifish, Fundulus heteroclitus
Authors: Peter R. E. , Macey M. J. , Gill V. E.
Published: January 2005

A stereotaxic apparatus and technique for electrode placement in forebrain nuclei of the killifish, Fundulus heteroclitus, is described. An atlas of forebrain nuclei is given. A new nuclear region in the telencephalon is described.
Electrophysiological evidence for rod‐like receptors in the gray squirrel, ground squirrel and prairie dog retinas
Authors: Green Daniel G. , Dowling John E.
Published: January 2005

Spectral sensitivities of the gray squirrel, Mexican and 13‐line ground squirrel and prairie dog were determined by electroretinography under both dark‐ and light‐adapted conditions. The dark‐adapted spectral sensitivity function obtained from intact eyes of these species peaks between 515—525 nm; however, when corrected for lens absorption or recorded from the lensless eye, it peaks near 500 nm and closely matches in shape a rhodopsin nomogram curve (λmax = 502 nm). Upon light adaptation all these retinas become relatively more sensitive to long‐wave stimuli (i.e., they show a small Purkinje shift). The light‐adapted spectral sensitivity function is broader than that obtained from the dark‐adapted eye, especially toward the longer wavelengths. We conclude that in all these species the dark‐adapted spectral sensitivity is mediated by a single, rhodopsin‐like photopigment and that light‐adapted sensitivity is mediated by two (or more) photopigments.
Synaptic patterns in the visual cortex of turtle: An electron microscopic study
Authors: Ebner Ford F. , Colonnier Marc
Published: January 2005

The part of turtle general cortex that receives afferent fibers from the dorsal lateral geniculate nucleus and that shows evoked potentials to light stimuli has been studied with the electron microscope. This cortex consists of an outer molecular layer, a perikaryal layer, and a subcellular layer lying on a row of ependymal cell bodies. Neurons in the perikaryal lamina are characterized by long spine‐bearing apical dendrites ascending through the outer molecular layer and short finer basal dendrites in the subcellular zone. Scattered neurons without apical dendrites occur in both the molecular and subcellular zones. Two types of dendritic spines can be distinguished. Some are large, have a complex irregular shape, contain a variety of membranous sacs and mitochondria, and occasionally, a single bundle of microtubules embedded in an electron‐dense background opacity. These large spines are the most common postsynaptic element in the outer third of the molecular layer, where they are located on the distal tips of the apical dendrites. Other spines are small, with a simple spherical distal enlargement that contains only electron‐dense fuzz. They are the most common post‐synaptic element in the lower two‐thirds of the molecular layer where they arise from the proximal portion of apical dendrites. Most synaptic contacts are found on the dendritic spines and are of the “round‐asymmetrical” type. Not infrequently “flat‐symmetrical” synapses are seen coupled to “round‐asymmetrical” contacts on individual large spines. The few contacts present on spine‐bearing dendritic shafts are of both types. Axo‐somatic contacts are mainly of the “flat‐symmetrical” variety. Thus the synaptic patterns on the principal cells of turtle visual cortex are remarkably similar to those found on pyramidal cells of mammalian neocortex. In addition, however, axon terminals, dendrites and glial (ependymal) processes were often seen to give rise to membranous pouches containing large vacuoles and invaginating into dendritic shafts or spines. Rarely, axon terminals were seen to form contacts, identical in appearance to synaptic contacts, on cell bodies in the ependymal lining. More frequently, unusual types of membrane differentiations were present at the site of apposition of the membranes of axon terminals and ependymal processes. They are interpreted as functional neuroependymal contacts.
Cytoarchitecture of the optic tectum in the nurse shark
Authors: Schroeder Dolores M. , Ebbesson Sven O. E.
Published: January 2005

The cytoarchitecture of the optic tectum of the nurse shark is described and related to the arrangements of afferents from retina, telencephalon and contralateral tectum. Its lamination is not pronounced when compared to tecta of most other non‐mammalian species but more comparable to those of mamals. The absence of highly differentiated cells such as pyramidal and true horizontal cells is perhaps correlated with the poor differentiation in general, including the apparent partial overlap of inputs. Some neurons near the midline were found to posses dendrites extending into the contralateral tectum.
Some aspects of synaptogenesis in the spinal cord of the chick embryo: A quantitative electron microscopic study
Authors: Oppenheim Ronald W. , Chu‐Wang I‐Wu , Foelix Rainer F.
Published: January 2005

We have quantitatively examined the development of synapses in the ventral part of the lumbar spinal cord of the chick from embryonic day 4 until adulthood. The first synapses occur on day 4 and are of the axo‐dendritic type; they are invariably located adjacent to the border between the intermediate and marginal zones. Initially there are more synapses in the presumptive white matter than in the motoneuron neuropil, but this trend is later reversed; however, we found numerous axo‐dendritic synapses throughout much of the ventrolateral white matter even in the adult stage. The first axo‐dendritic synapses always contain spherical synaptic vesicles and have symmetric membrane specializations. By day 7 a few of these synapses were found to have mixed populations of spherical and flattened vesicles and asymmetric membrane specializations. After hatching there are still considerably more axo‐dendritic synapses with symmetric membrane specializations.

Axo‐somatic synapses were first found on embryonic day 6 and were typically located on motoneurons lying adjacent to the marginal zone. These axo‐somatic synapses contain a few spherical synaptic vesicles and have symmetric membrane densities. Flattened synaptic vesicles were first found on day 10 and increased throughout development. Although a few axo‐somatic synapses with asymmetric membrane specializations were found at practically all stages, the symmetric type was always in the majority. An attempt was made to relate these observations with physiological, behavioral and neuroembryological findings from birds and other forms. For example, the fact that axo‐dendritic synapses always appear prior to axo‐somatic contacts would seem to rule out the role of somatic synapses in the initial induction of dendritic growth in the spinal cord.
The pulvinar nucleus of Galago senegalensis
Authors: Glendenning K. K. , Hall J. A. , Diamond I. T. , Hall W. C.
Published: January 2005

The present study was undertaken to analyze the connections of the pulvinar nucleus in a prosimian. The experiments, which rely on the Fink‐Heimer ('67) method for staining degenerating axons and their terminals, fall into two parts: first, the tracing of ascending tectal projections to the caudal thalamus and second, the tracing of projections from this thalamic target to the cortex. Large lesions of the superior colliculus resulted in dense degeneration in the caudal half of the inferior subdivision of the pulvinar complex. This pathway could be identified when the lesion was restricted to the superficial layers of the superior colliculus, signifying that it is a visual pathway. In general, the projections of the deep and superficial layers of the superior colliculus were distinct and in this respect Galago resembles Tupaia. The inferior pulvinar nucleus in turn projects to area MT, a conspicuous subdivision of the temporal cortex. The superior division of the pulvinar, in contrast to the inferior division, is not a major target of ascending projections from the superior colliculus and projects to the areas of the occipital and temporal lobe intercalated between areas MT and 17. When these results are compared with similar studies in nonprimates, notably studies of Tupaia, a striking difference in organization emerges. In Tupaia, and in distantly related mammals such as the squirrel, the target of the tecto‐pulvinar system includes area 18 adjacent to area 17. This feature is important since the two parallel projection systems seem to be related to each other in terms of the way in which the zero vertical meridian is spatially represented. However, in Galago the subdivision of the pulvinar receiving projections arising from the superior colliculus does not project to area 18. Area 18 is indeed the target of pulvinar projections, but these projections arise from that portion of the pulvinar which is not a recipient of ascending tectal projections. It is not easy to see how this primate organization, if indeed the Galago is representative of primates, evolved from the organization reflected in Tupaia.
An ultrastructural study of the red nucleus in the rat
Authors: Reid J. M. , Flumerfelt B. A. , Gwyn D. G.
Published: January 2005

The red nuclei of 14 adult male rats of the Wistar strain were prepared for electron microscopic study following perfusion with a mixture of aldehydes. Neurons of four size categories were identified in 1 μ Epon sections and their ultrastructural characteristics were studied in adjacent thin sections. Giant ( >40 μ) and large (20–40 μ) neurons are distinguished primarily by size and possess similar ultrastructural features: extensive areas of rough endoplasmic reticulum (RER), a prominent perinuclear Golgi complex, numerous mitochondria and pigment granules and a large, ovoid nucleus which occasionally contains intranuclear rodlets. Medium size neurons (20–25 μ) have less extensive, poorly organized RER and randomly distributed Golgi complexes. The nuclear envelopes of these cells fraquently show multiple invaginations and continuity with the RER cisternae. In small neurons (<20μ) the RER occurs as single or anastomosing strands while Golgi complexes and pigment granules are few. In both medium size and small neurons, aggregates of condensed chromatin are adherent to the inner nuclear membrane.

Three main types of synaptic terminals may be distinguished in the red nucleus: (1) small terminals with flattened vesicles and symmetrical densties (F terminals), (2) small terminals with rounded vesicles and asymmetrical densities (RS terminals), and (3) large (10–15 μ) asymmetrical, rounded vesical terminals which form multiple contacts along their length (RL terminals). The small neurons receive both F and RS terminals on their dendrites and infrequently on their cell somes. The large and giant neurons receive F, RS and RL terminals on their somes and proximal dendrites and F and RS terminals on their distal dendrites. The somas and dendrites of medium size neurons receive both F and RS terminals but RL terminals do not lie in relation to them. Spine contacts are common throughout the nucleus and occur on both somas and dendrites.
Taste pathways to hypothalamus and amygdala
Authors: Norgren Ralph
Published: January 2005

The projections of a third order gustatory relay in the dorsal pons of rats have been traced using tritiated proline autoradiography and antidromic activation of pontine neurons from electrodes in the thalamus and amygdala. Labelled axons collect in the central tegmental tract and ascend to the thalamic taste area in the medial extension of the ventrobasal complex. The majority of the fibers remain ipsilateral, but a few cross in the rostral pons and midbrain. The largest crossing occurs at the level of the thalamic termination. Many fascicles of fibers continue rostrally by passing beneath the thalamic taste area, piercing the medial lemniscus, and spreading out along the dorsomedial corner of the internal capsule (IC). The terminal field at this level caps IC from the subthalamic nucleus down into the far‐lateral hypothalamus. Labelled axons gradually penetrate through the internal capsule, and ramify throughout the underlying substantia innominata. This terminal zone extends laterally into the rostral end of the central nucleus of the amygdala, which is densely labelled to its caudal extremity. At the caudal end of the amygdala labelled fibers are visible in one component of the stria terminalis. These fibers can be followed over the dorsal thalamus into a smaller, but equally dense terminal area in the dorsolateral bed nucleus of the stria terminalis. The electrophysiological data demonstrate that pontine gustatory units can be antidromically activated by electrodes located in or near the central nucleus of the amygdala. Since many of the same units can also be driven from the thalamic taste area, at least some of the axons traced autoradiographically probably convey gustatory information to the hypothalamus and amygdala.
Receptive fields of barrels in the somatosensory neocortex of the rat
Authors: Welker Carol
Published: January 2005

Peripheral receptive fields of “barrels” in the somatosensory neocortex (SmI) of rats were determined with microelectrode recording and anatomical techniques. A method of flattening each hemisphere prior to embedding was devised so that the organization of layer IV could be seen through the full extent of SmI on a single section. All of the barrels in the rat are located within layer IV of SmI. Sinus hairs on the lateral and rostral face and furry buccal pad project to a continuous sheet of barrels in the head area of the contralateral SmI. The pattern of projections in this area indicates that each barrel receives information from one sinus hair. Large whisking vibrissae project to the largest celldense barrels and smaller non‐whisking sinus hairs project to smaller barrels that are relatively cell‐sparse. Barrels were also found outside of the head area in regions that receive projections from the forepaw and hindfoot. Receptive fields of these barrels are located on glabrous and hairy surfaces of the appendages that do not include any sinus hairs. Other parts of the body project to celldense areas of SmI that do not appear to contain barrels. Barrel subgroups and other somatotopic areas are separated by narrow barrel‐free zones. As a result of this pattern of contrasting cell densities, an outline of the rat's body is delneated within layer IV.
A somatotopic and functional representation of the respiratory muscles in the trigeminal and facial motor nuclei of the carp (Cyprinus carpio L.)
Authors: Luiten P. G. M.
Published: January 2005

The place of the cells innervating six most important respiratory muscles in the carp (Cyprinus carpio L.) were determined by means of the horseradish peroxidase technique. It was found that these muscles are represented in the rostral and caudal subdivisions of the trigeminal and facial motor nuclei. All connections were ipsilateral. The distribution of the various cell populations over the different subnuclei has been related to the function of the respective muscles in the respiratory cycle. On these grounds it could be concluded that muscles active in the contraction phase of respiration are represented in the rostral subnuclei, the expansion muscles in the caudal subnuclei. This arrangement appears to be a compromise between a somatotopic and functional organization.
Efferent connections of the caudate nucleus in the virginia opossum
Authors: Mickle John Parker
Published: January 2005

The efferents of the opossum's caudate nucleus were investigated by charting the fiber degenerations produced by electrolytic lesions in various parts of this nucleus. By the aid of a modified Fink‐Heimer procedure, degenerating fibers were traced from each of the lesions to the small globus pallidus in which they appeared to be distributed in an orderly dorsoventral pattern. Fibers From all lesion sites in the caudate nucleus were found to terminate in the entopeduncular nucleus. In the substantia nigra, caudatofugal‐fiber degeneration was confined in all cases to the rostral part of the pars reticulata, and was densest in the medial one‐half of this nucleus. Only from lesions in the ventromedial part of the caudate nucleus could degenerating fibers be traced to the nucleus ansae lenticularis. No fiber degeneration could be traced rostrally from the lesions, or to the putamen, red nucleus, subthalamic nucleus, or pons.
Postnatal maturation of subcortical projections from the prefrontal cortex in the rhesus monkey
Authors: Johnson Thomas N. , Enger Rosvold H. , Galkin Thelma W. , Goldman Patricia S.
Published: January 2005

Orbital and dorsolateral prefrontal lesions were performed on a series of rhesus monkeys at 2, 6, or 24 months of age. The consequent degeneration in the efferent pathways from these cortical regions to the caudate nucleus, the dorsomedial nucleus of the thalamus and adjacent structures was studied at 5‐ and 15‐day survival times by a modification of the Nauta‐Gygax method for tracing degenerating fibers. Following dorsolateral lesions, considerable numbers of black‐impregnated degenerating fibers were found in the parvocellular division of the dorsomedial nucleus and in the fiber bundles of the internal capsule and the subcallosal fasciculus at all ages. In contrast, the degree of Nauta‐Gygax degeneration in the anterodorsal sector of the head of the caudate nucleus was age‐dependent: degenerating fibers were found in increasing numbers from two months of age, when virtually none could be detected, to 24 months of age, when they appeared in relatively dense concentration. Similar results were obtained following orbital prefrontal lesions at the same three ages: degeneration in the magnocellular division of the dorsomedial nucleus of the thalamus and in the internal capsule were not related to age, but anterograde degeneration in the ventral and lateral capsular region of the caudate increased substantially with advancing age. Negative results with the Nauta‐Gygax technique in very young animals may not signify an actual absence of the connection in question, but our findings, together with those of other studies employing silver degeneration methods, at least suggest that in the primate, certain cortical efferents undergo maturational changes during postnatal life, a fact which may be related to the differential behavioral consequences of cortical injuries at different stages of development.
The facial motor nucleus of the opossum: Cytology and axosomatic synapses
Authors: Falls William M. , King James S.
Published: January 2005

The normal cytology and synaptic organization of the opossum facial motor nucleus was determined by use of Nissl preparations, Golgi impregnations, one‐micron plastic sections and electron microscopy. Neurons from all regions of the nucleus can be classified into three categories based on the size and shape of their perikarya, the distribution of Nissl substance and extent of their dendritic arbors. Large neurons (30–50 μ) exhibit numerous Nissl granules and their dendrites often span more than one‐half the width of the nucleus in the transverse plane. Their proximal dendrites measure 4–7 μ in diameter, taper to 0.5–2 μ and display few spines. Medium neurons (20–30 μ) can be distinguished from the large nerve cells by their size and their less extensive dendritic arbor. Proximal dendrites measure 4–7 μ in diameter, tapes to 0.5–2 μ and are realtively aspinous. Small neurons (10–20 μ)display a thin rim of cytoplasm which is either uniformly basophilic or achromatic. The dendrites of these neurons are relatively unbranched and taper from 4–5 μ proximally to 0.5–2 μ distally. Their axons give off one or two collaterals within the nuclear borders. More than one‐half the perikaryal membrane of large and medium neurons is covered by presynaptic profiles which were grouped into three primary categories based upon, differences in their vesicle shape (spherical, pleomorphic, or ellipsoidal). Only a few axosomatic contacts are present on small neurons. Further differentiation of axosomatic synaptic endings is suggested by differences in vesicle size, in pre‐ and postsynaptic membrane densities and in the size of the synaptic terminals. Vesicle size was determined by a cybergraphic tablet and a PDP‐12 computer system and is expressed as a mean area in nm2.
Desending pathways from the brain stem to the spinal cord in some reptiles. I. Origin
Authors: ten Donkelaar H. J.
Published: January 2005

In the present study the origin of the pathways descending from the brain stem to the spinal cord has been investigated in the reptiles Testudo hermanni, Pseudemys scripta elegans, Tupinambis nigropunctatus and Python reticulatus. These reptiles, using highly different types of progression, have been selected, because fundamental variations in the organization of the central motor apparatus are to be expected.

The origin of the descending pathways has been demonstrated by recording the occurrence of retrograde cell changes following hemicordotomies and by searching for labeled cells following injection into the spinal cord of the enzyme horseradish peroxidase.

In the reptiles studied the presence of interstitiospinal, vestibulospinal and reticulospinal pathways could be demonstrated. A crossed rubrospinal tract has been shown in the turtles and in the lizard, but could not be demonstrated in the Python. The presence of a direct tectospinal pathway could not be shown.
Descending pathways from the brain stem to the spinal cord in some reptiles. II. Course and site of termination
Authors: Ten Donkelaar H. J.
Published: January 2005

The course and termination of the pathways descending from the brain stem to the spinal cord have been studied by tracing the ensuing antero grade fiber degeneration, following appropriate lesions in the reptiles Testudo hermanni, Tupinambis nigropunctatus and Python reticulatus.

In these reptiles the presence of interstitiospinal, vestibulospinal and reticulospinal pathways has been demonstrated. A crossed rubrospinal tract has been shown in the turtle and lizard, but could not be demonstrated in the Python. The presence of a tectospinal pathway of any importance could not be shown. However, the tectum mesencephali has been found to project profusely to the brain stem reticular formation.

The interstitiospinal tract projects predominantly to the ipsilateral side of the spinal cord. The vestibulospinal projection, arising from the large‐celled nucleus vestibularis ventrolateralis, comprises a large uncrossed and a small decussating component.

The rubrospinal pathway terminates in a particular area of the spinal gray, i.e., the intermediate zone, whereas the interstitiospinal, reticulospinal and vestibulospinal tracts all terminate in the medial part of the ventral horn.

It appeared that the classification of descending pathways as advocated in mammals by Kuypers ('64) into lateral and medial systems can be readily applied to reptiles. The lateral system terminates in the dorsal and lateral parts of the intermediate zone, the medial system predominantly in the dorsomedial part of the ventral horn. This classification renders it likely that the absence of a lateral focus of termination as well as the absence of a rubrospinal tract in the Python, is correlated to the absence of limbs.

A comparison of experimental data concerning the systems descending from the brain stem to the spinal cord in amphibians, reptiles, birds and mammals suggests that these systems with regard to origin, course and termination have a basic pattern in common.
The neurons in the centromedian‐parafascicular complex of the monkey (Macaca mulatta): A Golgi Study
Authors: Hazlett James C. , Dutta Chitta R. , Fox Clement A.
Published: January 2005

The neurons of the nucleus centrum medianum and the neurons of the nucleus parafascicularis were studied in Golgi preparations of the adult monkey(Macaca mulatta)

The cell bodies of the principal neurons in the nucleus centrum medianum have a few somatic spines and vary in shape: some are cubical with protruding angles; some are egg‐shaped;some are elongated and sausage‐shaped. Four to six slightly branched dendrites of unequal thickness radiate from the cell body. Some dendrites extend for nearly 500 microns; all have dendritic spines.

In the nucleus parafascicularis there are two varieties of principal neurons:(1) neurons with somatic spines and(2) neurons without somatic spines. The neurons with somatic spines are most numerous. They have polygonal‐shaped cell bodies, prominent somatic spines and processes, larger than spines but considerably smaller than dendrites. These processes bear spines and are designated here “microdendrites.” Spines and occasionally a “microdendrite” are found on the axon‐hillocks. Five to six dendrites of unequal thickness emerge from the cell bodies. Some extend for more than 500 microns; all have prominent dendritic spines.

The neurons without somatic spines are relatively few. Usually three exceptionally long, slightly branched dendrites, one apical and two basal, emerge from their elongated, slim cell bodies. Some dendrites extend for more than 800 microns; all have a few scattered spines.

The Golgi type II neurons found in both of these intralaminar nuclei have small cell bodies and a few, relatively long, undulating dendrites, which bear bulbous dendritic appendages and beaded axon‐like processes. Distally on these dendrites, where the appendages and processes are more numerous, the dendritic appendages and axon‐like processes form complex entanglements. Beaded axons are found on some but not all of the cell bodies. Morphologically these neurons resemble the local interneurons that have been described in various thalamic nuclei.
Polarization of the avian retina. Ocular transplantation studies
Authors: Goldberg Stephen
Published: January 2005

The optic fiber layer of the avian retina, as seen in flat mounts, contains morphological markers of vertical and horizontal polarity. Optic vesicles were rotated in chick embryos prior to the appearance of the optic fiber layer. Later, the optic fiber pattern was examined to determine if its polarity was inverted, or upright or if its right‐left asymmetry changed.

Large grafts showed no tendency toward axial realignment, regardless of the stage of operation.

Moderate size grafts became realigned mainly by derotation. In this process the vertical axis of the graft showed a greater tendency to derotate than the horizontal axis. Thus, left‐to‐right transplants, when performed prior to embryonic stage 12, developed as left retinas with normally aligned vertical axes, regardless of the degree of operative rotation.

Small grafts mainly showed cross‐axial regulation, as opposed to derotation; the polarity of the horizontal axis became fixed prior to the vertical axis.

The equatorial zone of the optic vesicle, which lies about midway between the distal tip of the vesicle and the midline of the embryo, was included in moderate size, but not in small grafts. This zone appears critical in the transfer of morphological information to the developing retina.
Cortical cells projecting to the dorsal column nuclei of cats. An anatomical study with the horseradish peroxidase technique
Authors: Weisberg J. A. , Rustioni A.
Published: January 2005

The retrograde transport of horseradish peroxidase (HRP) has been used to label cortical neurons which give origin to descending projections to the dorsal column nuclei (DCN) in kittens and adult cats. HRP was injected unilaterally or bilaterally into the dorsal medulla at, or rostral to, the level of the obex, and, in most cases, retrogradely transported HRP was visualized in cortical neurons by incubation of serial 40 μm coronal or sagittal frozen sections. In the remaining cases, 1 mm coronal or sagittal slabs through the anterior part of the cerebral hemisphere were cut and incubated en bloc, and embedded in celloidin for sectioning (40 μm).

HRP‐positive neurons identifiable as the source of cortical projections to the DCN were layer V pyramidal cells whose largest diameter ranged from 20 to 45 μm: no “giant” cells were labelled. The cells appeared concentrated in the fore‐and hindlimb regions of the sensorimotor cortex and, to a lesser extent, in the second somatosensory area contralateral to the injected side. Labelled neurons were especially numerous in the upper bank of the cruciate sulcus and in the medial wall of the posterior sigmoid gyrus which respectively form parts of areas 4 and 3a (Hassler and Muhs‐Clement, '64). The number of labelled neurons progressively diminished in the first somatosensory area proper (areas 3b, 1 and 2). Ipsilaterally, fewer labelled neurons were present, mainly in areas 4 and 3a.

These results are in general agreement with previous anatomical and electrophysiological studies. It is suggested that previous results based upon lesions or electrical stimulation of the cerebral cortex in cats have failed to reveal adequately the cortical regions containing the bulk of the cells projecting to the DCN, since these regions have escaped selective experimental manipulation due to their relative inaccessibility.
Properties of ganglion cells in the visual streak of the cat's retina
Authors: Rowe Michael H. , Stone Jonathan
Published: January 2005

The properties of ganglion cells in the visual streak of the cat's retina have been investigated. Evidence is presented that the streak is formed principally, but not entirely, by a concentration of small‐bodied ganglion cells with the receptive field properties and slow‐conducting axons typical of W‐cells.
The development of the cerebellar cortex of the syrian hamster, Mesocricetus auratus. Foliation, cytoarchitectonic, golgi, and electron microscopic studies
Authors: Oster‐Granite Mary Lou , Herndon Robert M.
Published: January 2005

Although a number of investigations of abnormalities of cerebellar development have been carried out in the hamster, no detailed Golgi or ultrastructural studies of cerebellar development in this species have been reported. This report describes the development of the hamster cerebellar cortex from birth (day 0) through postnatal day 78, as studied by light, Golgi, and electron microscopic methods. Foliation patterns correlate with the expansion of the cerebellar layers and of total cerebellar area. Cytologic and morphologic development of the major cerebellar cell types–Purkinje, Golgi, basket, stellate, granule, and Bergmann glial cells–correlate with those of other species, such as the rat and mouse. Electron microscopic observations at selected developmental ages allow identification and classification of synapses in the early postnatal hamster. Parallel fiber and climbing fiber synapses are already present at birth. Although synaptogenesis probably continues through the first two postnatal months, all major cell types have developed initial synapses by postnatal day 6, at a time when little cellular maturation has occurred. By using gestational rather than natal age, close developmental correlations between hamsters and rat and mouse are possible. Since the gestational period of the hamster is only 16 days, the hamster cerebellum is less mature at birth than that of either the rat or mouse. Thus, the hamster is a convenient animal in which to investigate the effects of various procedures on early cerebellar development.
Evidence that at least some of the motor nerve cells that die during development have first made peripheral connections
Authors: Prestige M. C.
Published: January 2005

The paper sets out to determine whether the spinal motoneurons that die during the normal development of Xenopus tadpoles have been peripherally connected before death. The numbers of cells in the control ventral horns were compared with the numbers remaining after early (stage 50 or 52/53) amputation of the limb bud. Up to stage 52, there was no difference between the two sides, but thereafter the numbers on the amputated side fell away until at stage 57 none were left. Thus, as neurons mature, they become dependent for survival on contacting the limb. During this time, there was no difference between amputees and controls in the numbers of mitoses in that part of the ventricular layer that gives rise to ventral horn cells, indicating no change in proliferation. Thus, the numbers of ventral horn cells remaining after early amputation is a measure of the numbers of cells in the normal animal that are still independent of the limb (Phase I cells) and hence by subtraction, the other cells (post‐Phase I cells) are those that only survive by virtue of having contacted the limb. A graph of numbers of post‐Phase I cells shows a peak at stage 54 and thereafter declines as metamorphosis approaches. This is interpreted to indicate that a number of cells that survive at stage 54 by reason of peripheral contacts or connections in the limb subsequently themselves die, that is, that at least some of the cells that die during normal development have previously made contacts within the limb.
An electron microscope study of motoneurones and interneurones in the cat abducens nucleus identified by retrograde intraaxonal transport of horseradish peroxidase
Authors: Spencer Robert F. , Sterling Peter
Published: January 2005

Abducens motoneurones innervating the lateral rectus muscle and abducens interneurones projecting to the oculomotor nucleus have been studied in the cat by light and electron microscopy following labelling with horseradish peroxidase. Motoneurones ranged from 15–60 μm in diameter and typically contained circular nuclei with smooth or slightly irregular nuclear membranes and extensive cisternae of granular endoplasmic reticulum. Interneurones ranged from 25–50 μm in diameter and comprised two cytologically distinct cell types. One type was fusiform in profile and contained nuclei with fluted or deeply invaginated nuclear membranes and poorly developed granular endoplasmic reticulum. The other interneurone type resembled the motoneurones cytologically, having multipolar or circular profiles, smooth or slightly irregular nuclear membranes, and well developed cisternae of granular endoplasmic reticulum.

The densities with which boutons were distributed on the somata of motoneurones and interneurones were similar, as were the ratios of boutons containing spheroidal or flattened synaptic vesicles. Motoneurones varied significantly in the density with which boutons were distributed on their somata, and had greater densities on their dendrites than on their somata. Density was, furthermore, not correlated with motoneurone soma diameter. The proportion of spheroidal or flattened vesicle boutons on the somata of motoneurones was almost equal, with comparatively little variation between individual motoneurones. Motoneurone dendrites, however, with the exception of lateral dendrites, had a relatively higher proportion of boutons containing spheroidal synaptic vesicles. The lateral dendrites, which extend toward the medial vestibular nucleus, a known source of inhibitory afferents to the abducens motoneurones, had a higher proportion of boutons containing flattened vesicles.

The results indicate that abducens motoneurones and interneurones cannot be distinguished by any simple morphological criteria. The somadendritic distribution of boutons on motoneurones appears to be governed by certain broad rules.
Distribution of commissural afferents to the hippocampus of the rabbit
Authors: Hjorth‐Simonsen A.
Published: January 2005

The commissural connections of the hippocampus (fascia dentata and Ammon's horn) were investigated in the rabbit using a Fink‐Heimer silver impregnation method after the transection of either or both hippocampal commissures. In some cases additional sections were processed either with a histochemical method for acetyl cholinesterase or with the Timm‐Haug sulfide silver method.

The fibers to the fascia dentata arrive through the ventral commissure and terminate in a juxtagranular zone that corresponds to a relatively pale zone in acetyl cholinesterase preparations and to a dark zone in Timm‐Haug sulfide silver preparations. The degeneration is more dense in the middle of the Ushaped cross‐sectional profile of the fascia dentata than at the edges. This is particularly evident in the ventral portion of the fascia dentata. There is no evidence of commissural terminals in the layer of polymorphic cells. The commissural fibers to the Ammon's horn pass through both commissures. The fibers in the dorsal commissure terminate in the strata radiatum, oriens and pyramidale at their transition to the subiculum, in the septal part of the Ammon's horn. The molecular layer contains relatively little degeneration after transection of the dorsal commissure with the exception of the crossed entorhinal efferents to the rostral part. Fibers from the ventral commissure terminate in both the stratum oriens and the stratum radiatum. The degeneration in the stratum oriens is dense through the full extent of the layer, while that in the stratum radiatum is maximal in the regio inferior near the fimbria and less dense close to the fascia dentata and in the regio superior, with the exception of the antero‐rostral extreme of the latter. The density of degeneration in the stratum radiatum diminishes in the postero‐ventral direction except for degeneration at the subicular and dentate ends of the layer.

Evidence is presented for a powerful ipsilateral longitudinal association path terminating in the stratum radiatum of the regio inferior and in a minor adjacent portion of the dentate commissural zone.
The inferior olivary complex of marsupials
Authors: Watson Charles R. R. , Herron Paul
Published: January 2005

The inferior olivary complex (IOC) of marsupials was investigated to determine if correspondence exists between the IOC of marsupials and the IOC of eutherian mammals. We examined serial sections of the IOC of members of the eight major marsupial families: Didelphidae (Didelphis virginana, Philander opossum, Marmosa murina, and Caluromys sp.), Caenolestidae (Caenolestes obscurus and Lestoros inca), Dasyuridae (Antechinus flavipes, Dasyurus viverrinus and Sarcophilus harrisii), Peramelidae (Isodon obesulus and Perameles nasuta), Phalangeridae (Trichosurus vulpecula and Pseudocheirus peregrinus), Petauridae (Schoinobates volans and Petaurus breviceps), Vombatidae (Vombatus ursinus) and Macropodidae (Potorous tridactylus, Setonix brachyurus, Macropus eugenii and Macropus rufus).

Evidence is presented that the principal nucleus (PIO) and dorsal nucleus (DIO) of the marsupial IOC are directly comparable to nuclei in eutherians. Nauta degeneration studies on the pattern of termination of spinal and rubral afferents in Trichosurus vulpecula support arguments for homology between the PIO and DIO of marsupials and of eutherians. However the probable homologue of the eutherian medial nucleus (MIO) has certain features that are unique to marsupials; while it can be divided into the same subnuclei found in eutherians (subnuclei a, b, c and the cap of Kooy) most of the cells of the marsupial medial nucleus homologue are located lateral to the PIO. The few cells of the MIO homologue that lie medial to the PIO are connected in some marsupials to the main lateral portion by a sheet of cells that lies ventral to the PIO. For this reason we propose that the medial nucleus homologue be named the ventral nucleus (VIO) in marsupials. Because of the ventral position occupied by medial nucleus cells during development in both eutherian and marsupial mammals, the term VIO could also be properly applied to the eutherian MIO as well.