bluuebunny/crossref_metadata_2025 huggingface dataset:
Fiber analysis of the feline inferior cardiac sympathetic nerve
Authors: Emery Dennis G. , Foreman Robert D. , Coggeshall Richard E.
Published: January 2005

The left inferior cardiac nerves of nine adult cats were examined with the electron microscope. Electrical recordings were also made from four of these nerves. Most of the nerves contained between 25,000 and 40,000 unmyelinated fibers and 30 to 150 myelinated fibers. The diameters of the unmyelinated fibers ranged from 0.1 μ to 1.8 μ with mean diameters ranging from 0.47 to 0.78 μ in the various nerves. The myelinated fibers ranged in diameter from 1 μ to 9 μ with a mean diameter of approximately 3 μ. Electrical recordings showed two peaks in both the C fiber and the Aδ fiber compound action potentials. Conduction velocities of the two C fiber peaks were approximately 0.7 and 0.9 m/sec. The two groups of Aδ fibers had conduction velocities of approximately 7 and 16 m/sec.
Pallidothalamic projections in the rat
Authors: Severin C. M. , Young P. A. , Massopust L. C.
Published: January 2005

The purpose of this investigation was to examine pallidofugal projections to the thalamus of the rat using a selective silver degeneration method and autoradiography. Degenerating pallidothalamic projections emerging from the anterior part of the pallidum formed two diffuse groups of fibers; one coursed ventromedially directly through the internal capsule without forming a lenticular fasciculus and terminated uniformly in the reticular, VA, VD, VM and the medial part of the VE. The other group coursed ventrolaterally in the internal capsule and, without forming an ansa lenticularis, entered the zona incerta, swept medially through and ventral to the medial lemniscus, and terminated in the medial part of the VE and throughout the VD. Degenerating fibers from both of these groups also terminated in the rhomboid, gelatinous, and medial dorsal nuclei of the thalamus. Fibers from the intermediate and posterior parts of the pallidum crossed the internal capsule in diffuse bundles and terminated in the medial and posterior zones of the reticular nucleus respectively. Most of the fibers passed through the reticular nucleus and terminated uniformly in the VA, VD, VM and the ventral portion of the VE. Some terminated in the medial and midline thalamic nuclear groups. The character of terminal degeneration differed markedly. In the ventral aspect of the VE it had a fine dust‐like appearance whereas in the VA, VD, and VM it was coarsely granular. Autoradiography confirmed the course and terminations described above except that reduced silver grains were not observed in the rhomboid, gelatinous and medial dorsal nuclei of the thalamus. Also, autoradiography confirmed that the dust‐like terminal degeneration in the ventral VE was of the anterograde type since the leucine label was concentrated in precisely the same area.
Trans‐glial channels in ventral nerve roots of crayfish
Authors: Shivers Richard R. , Brightman Milton W.
Published: January 2005

The sheath around the roots of the sixth abdominal ganglion in the yentral nerve cord of the crayfish consists of concentric layers of thin glial processes alternating with wide clefts containing filamentous connective tissue. Regions of each glial lamella are perforated by single, short, tubular channels: the trans‐glial channels. In thin plastic sections examined in the electron microscope, the channels appear as slits that are 240 Å wide and 450–550 Å long which traverse glial lamellae less than 1,500 Å thick. Branched tubular channels cross glial sheets that are thicker than 1,500 Å. The thickest glial wrap is adaxonal; it closely encapsulates individual axons and its cell membrane is separated from the axolemma by a collagen‐free space of only 150 Å. The adaxonal glial cytoplasm contains unique, three‐dimensional networks of interconnected tubules. Separate tubular lattices occur along these thicker processes.

In replicas of freeze‐fractured sheaths, the outer half of the plasma membrane belonging to the thin glial sheets exhibits many volcano‐like protrusions which represent cross fractures through the necks of trans‐glial channels. Corresponding depressions on the inner half of these membranes are sites where the plasma membrane invaginates to form the channels. Although some channels are randomly dispersed, others are lineraly positioned in restricted areas across successive glial layers. The number of channels is far more readily appreciated in replicas than in thin sections. The average frequency of channels is 16 per μ2 (range 8 to 33) in normal roots and does not differ significantly from the average of 13 per μ2 in proximal stumps of roots fixed three to four weeks after the roots were cut. The channels are not precisely aligned from one glial layer to the next but do appear to coincide approximately with the adaxonal tubular lattice. The combination of trans‐glial channels and adaxonal tubular lattices may provide a complex conduit that could facilitate a rapid, passive flow of electrolytes and nutrients across the nerve sheath to the axonal surface. Horseradish peroxidase solutions bathing the ventral roots enter the trans‐glial channels, extracellular clefts and finally the tubular lattices. This distribution supports the proposed role of the channels in a rapid extracellular passage of solutes. The channel profiles have a range of forms consistent with the supposition that they are not static but continually reforming.

There are indications that, proximal to the cut, the areas of glial plasma membrane with channel profiles contain more junctional complexes between regenerating cells than between glial cells of normal sheaths. The channel profiles and aggregates of particles belonging to junctions are closely associated when they occupy the same region of the membrane.
Anatomical distribution of estrogen target cells in the avian CNS: A comparison with the mammalian CNS
Authors: Martinez‐Vargas M. C. , Stumpf W. E. , Sar M.
Published: January 2005

The distribution of labeled cells was investigated in the brain of the ring dove one hour after administration of 3H‐estradiol. Major areas of concentration of labeled cells were found in (1) the preoptico‐strial region: nucleus preopticus medialis and nucleus interstitialis of the dorsal olfactory projection, (2) the basal hypothalamic region: nucleus hypothalamicus posterior medialis and nucleus inferior, (3) the amygdaloid region: nucleus taeniae and adjacent portions of the archistriatum, and (4) the midbrain: substantia grisea surrounding the nucleus mesencephalicus lateralis, pars dorsalis. The findings support the phylogenetic homologies between the avian nucleus interstitialis of the stria dorsal olfactory projection and the mammalian nucleus interstitialis of the stria terminalis, the avian nucleus hypothalamicus posterior medialis and the mammalian nucleus ventromedialis hypothalami, as well as the avian nucleus inferior and the mammalian nucleus infundibularis‐premammillaris ventralis. The results also suggest that the nucleus taeniae and adjacent portions of the archistriatum correspond to the nucleus medialis and other more differentiated labeled areas of the mammalian amygdala.
The time of origin and the pattern of survival of neurons in the isthmo‐optic nucleus of the chick
Authors: Clarke P. G. H. , Rogers L. A. , Cowan W. M.
Published: January 2005

The time of origin of the cells in the isthmo‐optic nucleus (ION—the nucleus of origin of centrifugal fibers to the avian retina) has been determined in the chick by a variant of the cumulative labeling method, using 3H‐thymidine autoradiography. All the neurons of the ION are generated (i.e., pass through their last phase of DNA synthesis) over a 50‐hour period between the latter part of the fifth and the seventh days of incubation (stages 28–31 of the Hamburger and Hamilton [′51] series) but the cells come to be assembled with in the nucleus along a distinct temporo‐spatial gradient. The earliest‐formed cells occupy the ventrolateral part of the nucleus while the last neurons to be generated come to lie along its dorsomedial margin.

When the nucleus is numerically complete, around the eleventh day of incubation, it contains about 22,000 neurons, but between the thirteenth and seventeenth days (stages 39 through 43) this number is reduced by nearly 60% to about 9,500 cells. Following the radical extirpation of one optic cup or the circumscribed removal of the neural retina early on the third day of incubation, the cell loss in the contralateral ION is greatly accentuated, so that by the eighteenth day of incubation no cells remain in the nucleus. Serial counts of the numbers of cells in the nucleus on the side of the eye (or retinal) removals show that it, too, undergoes additional cell degeneration, so that by the end of the phase of naturally occurring neuronal loss, only about half the normal number of cells persist in these experimental animals.
The development of the isthmo‐optic tract in the chick, with special reference to the occurrence and correction of developmental errors in the location and connections of isthmo‐optic neurons
Authors: Clarke P. G. H. , Cowan W. M.
Published: January 2005

The development of the centrifugal projection to the chick retina in the isthmo‐optic tract (IOT) has been studied by the retrograde transport of the enzyme marker horseradish peroxidase (HRP) injected into the eye at various times during the incubation period.

Some neurons in the isthmo‐optic nucleus (ION — the cells of origin of the IOT) can first be labeled from the eye following injections on the tenth day of incubation; after injections on the twelfth day or later, about 95% of the neurons can be so labeled. It follows from this that the axons of virtually all the neurons in the ION (including the 60% which normally degenerate between the thirteenth and seventeenth days of incubation) reach the contralateral eye. Since in 12‐day old embryos the IOT is between six and seven millimeters in length and HRP can be identified in the perikarya of ION neurons within three and one‐half hours, the rate of retrograde transport in the system must be of the order of 48 mm/day. A similar time is required for HRP to appear in the perikarya of ION neurons in post‐hatched chicks in which the length of the IOT is estimated to be about 14 mm. This suggests that at some time during the latter half of the incubation period there is a significant acceleration in the rate of retrograde transport, similar to that found for anterograde axonal transport in the chick and rabbit visual systems.

In addition to labeling neurons in the contralateral ION, intraocular injections of HRP before the sixteenth day of incubation label a significant number of cells (up to 650) which lie outside the borders of the nucleus, and a small number (10–100) in the ipsilateral ION. About 90% of the ectopic neurons and all of the cells in the ION which send their axons aberrantly into the ipsilateral eye, degenerate some time after the fifteenth day of incubation, apparently because they either do not make appropriate connections within the retina or else fail to receive an appropriate input from the optic tectum. After early removal of one optic cup, the number of neurons in the ipsilateral ION that can be labeled by HRP injected into the surviving eye is greatly increased (involving as many as 50% of the cells in the nucleus). Despite the fact that the axons of these cells reach the retina (albeit of the “wrong” side) the cells do not survive beyond the seventeenth day of incubation. However, during the period in which their axons are in the retina they appear to interfere with synapse formation by the axons of the neurons in the contralateral (“correct”) ION; only about half the normal number of ION neurons survive under these circumstances. These findings suggest: (i) that certain types of errors may be common during neural development, (ii) that they are generally transitory, being recognized and eliminated at later stages in development, and (iii) that although transitory, some errors may have long lasting sequelae.
The facial motor nucleus of the opossum: Synaptic endings on dendrites
Authors: Falls William M. , King James S.
Published: January 2005

The diameters of dendrites of large, medium and small neurons (Falls and King, '76) were measured from Golgi impregnations of the opossum facial motor nucleus in order to classify dendritic profiles sectioned in the transverse plane in electron micrographs. Three categories of dendrites are described: (1) proximal (4–7 μ in diameter); (2) intermediate (2–4 μ in diameter) and (3) distal (0.5–2 μ in diamter). The distribution of axodendritic synaptic endings was determined, recognizing that the neuronal source of individual dendritic profiles when seen in the transverse plane of section cannot be absolutely determined in view of the overlap in size of the dendrites issuing from the three types of neurons. Presynaptic terminals were categorized according to vesicle shape (spherical, pleomorphic or ellipsoidal), vesicle size, terminal size, junctional characteristics and post synaptic distribution. The vesicle size is expressed as a mean area (nm2) and was determined by using a cybergraphic tablet and a PDP‐12 computer system.

In any given plane of section, synaptic terminals cover most of the membrane of proximal dendrites and decrease in number as intermediate and distal dendrites are encountered. In Golgi impregnations four classes of afferent fibers which ramify among the dendrites of facial neurons can be distinguished. As yet, their sources have not been identified. Possible sites of origin for presynaptic profiles are discussed in the context of previous light microscopic findings.
The supraoptic nucleus and the supraopticohypophysial tract in the monkey (Macaca mulatta)
Authors: Luqui Ivan J. , Fox Clement A.
Published: January 2005

The observations here on Golgi material are based on the study of fortunate impregnations in one horizontally sectioned and one frontally sectioned series found in the collection of Golgi preparations of the adult monkey brains (Macaca mulatta) available in this laboratory.

The soma of the large supraoptic neurons have jagged protrusions and irregular crevices which give their surfaces a craggy appearance. Also they have a few somatic spines. Their dendrites, which usually arise from two or three dendritic trunks, emerging from the cell body, are moderately branched and have occasional dendritic spines. The axon emerges from a conical elevation either on the soma or a dendrite and is directed towards the supraopticohypophysical tract.

In the present material there are a few neurons of the supraoptic nucleus impregnated that are definitely smaller than the larger neurons. They have short beaded axons, ending in the supraoptic nucleus a short distance from their point of origin.

In the horizontal sections the supraopticohypophysial tract fibers can be seen passing over the posterior aspect of the optic tract. In the frontal sections, this fan‐shaped tract, wide above and constricted below, can be followed into the median eminence. Some of these axons in their intrahypothalamic course have short beaded collaterals.

Electron micrographs reveal: (1) endings with spherical synaptic vesicles and endings with flattened synaptic vesicles synapsing on neurosecretory axons in the supraoptic nucleus; (2) a few myelinated fibers containing neurosecretory granules in the intrahypothalamic portion of the supraopticohypophysial tract.

As can be seen in both Golgi and electron microscopic preparations the presence of fibrous astrocytes in the supraoptic nucleus and their abundance in the hypothalamic portion of the supraopticohypophysial tract is characteristic of this neurosecretory system. In the nucleus and in the tract processes of the fibrous astrocytes are intimately associated with neurosecretory fibers.
Functional organization in the visual cortex of the golden hamster
Authors: Y‐C Tiao , Blakemore Colin
Published: January 2005

The visual cortex of the golden hamster was studied by means of multi‐unit and single unit recording, which revealed three separate retinotopic maps of the visual field in the posterior cortex. V1, corresponding to cytoarchitectonic area 17, has the contralateral temporal field represented medially, the central visual field (extending about 10 deg ipsilateral) represented laterally and the lower field anteriorly. The borders of the map, especially for the upper field, seem to be more restricted than the whole visual field available to the contralateral hemiretina: V1 probably does not represent the extreme periphery of the field. A large fraction of V1 has binocular input, for up to about 50 deg lateral to the vertical midline. There is a retinotopic reversal near the representation of the vertical midline where V1 meets V2 (corresponding to the more lateral “area 18a”). There is another retinotopic reversal at the extremity of the contralateral field representation, where V1 meets Vm (the medial visual area, corresponding to “area 18”) V2 and Vm each contain a reduced mirror image version of the map in V1. Almost all isolated single units in V1 have receptive fields that can be classified as radially symmetrical (60%) or asymmetrical (35%) Symmetrical fields have ON (13%) OFF (4%) ON‐OFF (30%) or “SILENT” (12%) central areas when plotted with flashing spots. There are minor but not striking differences between these groups in their field sizes, velocity preferences and so on. They almost invariably prefer moving to stationary stimuli but are not selective for orientation or direction of movement. Asymmetrical fields are of four types, three of which (type 1, 11% type 2, 17% and type 3, 2%) are orientation selective and resemble simple, complex and hypercomplex cells in the cat cortex. Some of these have direction as well as orientation preference. Axial movement detectors (5%) have a selectivity for one axis of motion, and thus prefer one orientation of edge, but respond equally well to movement of a spot. Vertical and horizontal orientation preferences, especially the latter, are much the most common. There is some evidence of clustering of cells according to receptive field type and, possibly, preferred orientation. Asymmetrical cells are, relatively, somewhat rarer in the deeper cortical layers. Within the binocular segment, fully 89%of cells are binocularly driven and the receptive fields are similar in the two eyes. Receptive fields tend to increase in size away from the area centralis representation and, in a complementary fashion, the magnification factor decreases from up to 0.1 mm/deg at the area centralis representation to about 0.02 mm/deg for the peripheral field.
Functional organization in the superior colliculus of the golden hamster
Authors: Y‐C Tiao , Blakemore Colin
Published: January 2005

The superior colliculus of the golden hamster was investigated by means of multi‐unit and single unit recording. The retinotopic map, which probably embraces a projection from the entire retina of the contralateral eye, is organized as in other vertebrates, with the central field represented in the anterior colliculus, the upper field medially. Magnification factor is fairly uniform and is about 0.02 mm/deg. There is a small binocular segment (where almost half of all neurones have input from the ipsilateral eye) in the anterior colliculus, representing the area of field around the area centralis and the anterior pole of the field. In the more superficial layers, units have small (about 10 deg diameter) receptive fields, which can be classified as symmetrical, responding to slow movement (80%) very fast movement detectors (6%) directional movement detectors (13%) and axial movement detectors (%) In the deeper layers, below the stratum opticum, receptive field size increases dramatically and many cells habituate rapidly, making them sensitive only to new events. Receptive fields can be classified as movement detectors (89%) directional movement detectors (10%) and axial movement detectors (2%). All directional receptive fields, at least in the upper visual field, have an upward component in their directional preferences. About 42% of deeper layer cells have somatic sensory input, responding to light touch on the fur or whiskers of the contralateral half of the body. Some 5% of cells respond to complex sounds on the contralateral side of the animal. Many of these somatic and auditory cells also have visual receptive fields and, throughout the colliculus, there is general correspondence between the maps of visual space, auditory space and the body surface. This correlation may be important in the regulation of orienting behaviour towards novel peripheral stimuli.
Regeneration of Müller and Mauthner axons after spinal transection in larval lampreys
Authors: Rovainen Carl M.
Published: January 2005

The regeneration of large unmyelinated axons following transection of the spinal cord was studied in small larval sea lampreys (Petromyzon marinus) Individual Müller and Mauthner axons normally occur in a characteristic pattern in the spinal cord, but their positions were altered in the first several segments caudal to the lesion following regeneration. Müller axons grew out of the ventral tracts and sometimes looped back towards the brain or crossed the midline; maximum misdirection of axons occurred near the site of transection. Mauthner axons frequently bifurcated. Despite the aberrant and incomplete regeneration of axons, the larvae exhibited normal coordinated swimming, crawling, and coiling behavior.
Efferents from medial basal forebrain and hypothalamus in the rat. II. An autoradiographic study of the anterior hypothalamus
Authors: Conrad Lily C. A. , Pfaff Donald W.
Published: January 2005

Using tritiated amino acid autoradiography, the efferent projections of the anterior hypothalamic area (AHA) were studied in albino rats.

Axons from AHA neurons were not confined to local projections in the hypothalamus. Ascending AHA axons ran through the preoptic region, joined the diagonal band and distributed in the lateral septum. Descending AHA efferents within the hypothalamus coursed in a bundle ventromedial to the fornix. Projections were observed to the dorsomedial, ventromedial, arcuate and dorsal premammillary nuclei, and to the median eminence. Sweeping dorsomedially in the posterior hypothalamus, some AHA axons distributed in the central grey. AHA axons staying ventral projected to the supramammillary region, ventral tegmental area, raphe nuclei and midbrain reticular formation. Other AHA efferents distributed to the periventricular thalamus, to the medial amygdala via the stria terminalis or supraoptic commissure, and to the lateral habenula through the stria medullaris.

For comparison with the AHA, efferent projections from the paraventricular nucleus (PVN) and from the ventromedial nucleus and adjacent basal hypothalamus (VMR) were studied. Projections from PVN neurons were not restricted to the median eminence and neurohypophysis. PVN efferents also distributed to many of the same regions as did those of the AHA but had somewhat different fiber trajectories and longer descending projections. VMR efferents were more widespread than those of the AHA, with projections extending into the lateral zona incerta and pontine reticular formation.

Projections from the AHA were distinct from those of the medial preoptic area (mPOA). For example, while AHA axons descended in a bundle ventromedial to the fornix, mPOA axons ran in the medial forebrain bundle. Such anatomical differences may underlie experimentally demonstrated functional differences between the mPOA and AHA, for instance, in mediation of male and female sex behaviors.
Axonal guidance of developing optic nerves in the frog. II. Electrophysiological studies of the projection from transplanted eye primordia
Authors: Constantine‐Paton M. , Capranica Robert R.
Published: January 2005

When a primordial eye was transplanted to the ear position in Rana pipiens embryos, the optic nerve from the ectopic eye penetrated the medulla and invariably established a tract in the dorsolateral white matter of the ipsilateral spinal cord. In response to visual stimulation of the transplanted eye, extracellular recordings with metal microelectrodes were conducted within the spinal cords of post‐metamorphic animals.

Visual activity in the spinal cord could only be recorded in those experimental animals in which the transplanted optic nerve succeeded in penetrating the medulla. This activity was frequently encountered in the gray matter of the cord well below the dorsolateral position of the transplanted optic tract. The discharge characteristics and adaptation properties of the visual activity were often similar to that of optic nerve fibers from normal eyes suggesting that axons or their collaterals branch off from the transplanted optic tract and arborize within the spinal cord. However, occassionally stimulation of the transplanted eye evoked activity with adaptation and/or response characteristics unlike that of normal optic nerve fibers.

Visual activity in the spinal cords of our experimental animals could be driven by moving small dark objects within circumscribed regions in the visual field of the transplanted eye. However we were unable to find any evidence of a systematic mapping of the transplanted retina within these abnormally penetrated spinal cords.
Areal changes in mouse cortical barrels following vibrissal damage at different postnatal ages
Authors: Woolsey Thomas A. , Wann Janice R.
Published: January 2005

The normal cytoarchitectonic pattern of barrels in layer IV of mouse SmI face cortex is altered by early damage to the mystacial vibrissae (Van der Loos and Woolsey, '73). In the present study, the middle row of vibrissae (row‐C) on one side of the face in groups of Swiss mice was cauterized on the day of birth (postnatal day [PND] – 1) or on PND's – 2, 3, 4, 5, 7, 10, 12, 15, 20 and 30; littermates in each group served as controls. All animals were perfused on PND‐60 and the brains sectioned parallel to SmI layer IV. For each specimen, the posteromedial barrel subfields (PMBSF) of the two hemispheres were reconstructed with a camera lucida and the cross‐sectional areas of individual barrels measured using a small computer.

The findings are: (1) The hemispheres ipsilateral to the vibrissal damage are quantitatively indistinguishable from the littermate controls indicating that the ipsilateral hemispheres in lesioned animals can serve as controls for observations of the type reported in this paper. (2) There are no consistent differences in the cross‐sectional areas of the PMBSF's as a whole in the hemispheres ipsi‐ and contralateral to the peripheral damage, suggesting that there is no net loss of cortex as a result of the lesions. (3) The contralateral row‐C barrels are reduced in size. Expressed as a percentage of normal values; row‐C is reduced to 17% for animals lesioned on PND‐1, 16% on PND‐2, 38% on PND‐3, 52% on PND‐4, and 79% on PND‐5; on PND‐7 and later the cross‐sectional areas of row‐C barrels are normal. This implies that the barrel field of the SmI face cortex becomes progressively refractory to the effects of peripheral damage during the first postnatal week and in the period prior to PND‐6, an intact periphery is necessary for normal cortical development. (4) In every case, the decreased cross‐sectional area of row‐C is accompanied by precisely increased cross‐sectional areas of the barrels in adjacent rows‐B and D. In the case of the restricted peripheral damage which we produced, there is a “compensation” in the contralateral hemisphere, which can be correlated with patterns of the specific thalamocortical projections.
A study of afferent input to the inferior olivary complex in the rat by retrograde axonal transport of horseradish peroxidase
Authors: Brown James T. , Chan‐Palay Victoria , Palay Sanford L.
Published: January 2005

Under direct visualization, minute amounts of horseradish peroxidase were injected by controlled air pressure through glass micropipettes into the inferior olive of the albino rat. Well localized unilateral injections were obtained, without damage to other brainstem areas or spread into the adjacent reticular formation. After 24 to 36 hours, the entire brain and spinal cord were examined by light microscopy for labelled neurons supplying afferents to the inferior olive.

With few exceptions, labelled somata rostral to the inferior olive were found ipsilateral to the injection site, the greatest number occurring in the subparafascicular nucleus and central gray substance around the caudal third ventricle, in the N. of Forel's field, Nn. of Darkschewitsch and Cajal, and adjacent reticular formation, and in the Edinger‐Westphal nucleus. Labelled cells were also noted in the sensorimotor cortex, red nucleus, peri‐aqueductal gray and all subdivisions of the pretectal complex. Caudal to the olive, labelled neurons were located primarily on the contralateral side in the lateral reticular nucleus, dorsal column nuclei and nucleus proprius of the spinal cord. At the level of the olive, numerous labelled cells occurred bilaterally, but mainly contralateral to the injection site in the lateral and interpositus nuclei of the cerebellum. A smaller number were seen in the N. prepositus hypoglossi and in the medial and spinal subdivisions of the vestibular complex ipsilaterally, in the N. spinal tract of V contralaterally, and in the gigantocellular reticular nucleus bilaterally. A few neurons in the N. raphe obscurus were also labelled. No positive cells were found in the caudate nucleus, globus pallidus, locus coeruleus, or medial cerebellar nucleus.

The results are compared and contrasted, region by region, with previous studies of afferent olivary pathways and, where possible, correlations are made with physiologic data.
Neurons in layer I of the developing occipital cortex of the rat
Authors: Bradford R. , Parnavels J. G. , Lieberman A. R.
Published: January 2005

This paper describes the neurons in layer I of the rat occipital cortex, and traces postnatal changes in the numbers and morphology of the different cell types therein. Golgi‐Cox and Nissl material from adults and from 0.5, 2, 4, 6, 8, 10, 11,12, 13, 14, 15, 16, 18, 20, 24, 28 and 35 day‐old rats, was utilized. Horizontal, vertical and classical non‐pyramidal cells and cells without axons were recognized.

Horizontal cells included foetal horizontal cells (Retzius‐Cajal cells) and persisting horizontal cells. The former were fully differentiated and numerous at birth and were bipolar, with dendrite and axon extending from opposite poles, and fine ascending (verticle) branches. Some such cells possessed two axons. Almost all degenerated and disappeared over the first two to three postnatal weeks. An analogy with Rohon‐Beard cells is drawn and it is suggested that these cells receive an early input which is subsquently withdrawn and/or concentrated cells receive an early input which is subsequently withdrawn and/or concentrated on cells in deeper layers. There is no evidence of transformation of foetal to persisting horizontal cells, which are not numerous and most commonly give rise to two dendrites from opposite perikaryal poles.

Vertical cells, with spinous dendrites and descending axons, differentiate and reach adult numbers by the end of the first postnatal week. Classical non‐pyramidal cells include spinous and spine‐free varieties, resemble those in deeper layer, and are mature by the end of the third postnatal week. In the upper stratum of layer I are small number of cells without axons.
Growth of the adult goldfish eye. III. Source of the new retinal cells
Authors: Johns Pamela Raymond
Published: January 2005

The manner in which new cells are added to the growing adult goldfish retina was examined using 3H‐thymidine radioutography. Cell proliferation leading to the formation of neurons is restricted to the retinal margin at the ora terminalis. New retina is added in concentric rings, with slightly more growth dorsonasally. The rate of cell addition is variable, averaging 12,000 cells/ day. These new cells account for about 20% of the total increase in retinal area; the remaining 80% is due to hypertrophy, or expansin, of the retina. In contrast to all of the other retinal cells, the rods do not appear to participate in the retinal expansion. This hypothesized immobility of the rods would create a shearing strain between the retinal layers resulting in a shift in their position relative to the other cells. Were they to maintain synaptic contacts with the same horizontal and bipolar cells, the rod axons would have to be elongated peripherally or the post‐synaptic cell dendrites displaced centrally. Since neurons with this morphology have not been found in the goldfish retina, these observations suggest that the rods must be changing their synaptic connections as the retina grows.
Incorporation of 3H‐fucose into nerve and glial cells: Assessment by electron microscopic autoradiography
Authors: Reisert I. , Wagner H.‐J. , Pilgrim Ch.
Published: January 2005

Incorporation of 3H‐fucose into hypothalamic tissue of rats was studied between ten minutes and seven days after intraventricular injection. In EM autoradiographs grain densities over perikarya of neurons, astro‐ and oligodendroglia, and neuropil were evaluated. Grain densities were consistently higher over both types of glial cells as compared to neurons. The glia/neuron ratio was especially high after short experimental intervals and declined with increasing time intervals. Concomitantly there was an increase of grain density over the neuropil. The discussion concentrates on the methodical aspects which have to be considered in interpreting the autoradiographic data. It is concluded that both astroglia and oligodendroglia exhibit a considerably higher synthesis rate of glycoproteins per unit volume than nerve cells. The implications of the results for the interpretation of biochemical data on glycoprotein metabolism of brain tissue are discussed.
The locus and cytoarchitecture of the projection areas of the olfactory bulb in Macaca mulatta
Authors: Turner Blair H. , Gupta Kailash C. , Mishkin Mortimer
Published: January 2005

A study was made of the normal and experimental anatomy of the olfactory system of the young adult male rhesus monkey. The cytoarchitecture of the central olfactory areas was studies with cell and fiber stains, while the extent and pattern of the projections of the olfactory bulb were determined by the Fink‐Heimer and autoradiographic methods. The brain of one animal that had sustained damage to the olfactory bulb two days prior to sacrifice, and of one that had a transection of the olfactory tract ten days prior to sacrifice, were processed with the Fink‐Heimer technique. The first of these and four others received injections of 3H‐proline or 3H‐leucine into the olfactory bulb, and following a survival period of 18 hours, or 2, 4, 12, or 20 days, their brains were proceessed with the autoradiographic technique. The results were the same for both experimenal methods and for all survivalperiods.

The projections of the olfactory bulb in this microsmatic animal are entirely ipsilateral. All of the structures that receive direct olfactory afferents have a laminar organization except for the anterior olfactory necleus, which is laminated only in its anterior, peduncular, portion. While the olfactory bulb projects to the entire extent and depth of the naterior olfactory nucleus, the olfactory afferents of all other structures are confined to layer IA of the plexiform layer. These structures are: all divisions of the olfactory tubercle; the frontal and temporal prepiriform cortices; the oral, medial, and dorsal divisions of the superficial amygdaloid nucleus; and polar and anterior entorhinal cortex. The rhesus monkey does not have a recognizable accessory olfactory bulb, and no projectiosns were seen to the taenia ecta or the ventral division of the superficial amygdaloid nucleus. With these exceptions, the projections of the olfactory bulb in the rhesus monkey are similar to those in macrosmatic species.
Some claustro‐cortical connections in the cat and baboon as studied by retrograde horseradish persocidase transport
Authors: Riche D. , Lanoir J.
Published: January 2005

1. The mammalian Claustrun (Cl) is a convergent multisensory structure of unknown function, and disputed ontogenetic origin. Its cortical projections, hitherto unknown, have been studied in cat and baboon by means of the horseradish peroxidase (HRP) technique. HRP was injected into the gyrus proreus (frontal eye field) of cats, and separately into the frontal eye fields, visual areas, and motor‐premotor areas of the baboon cortex.

2. Differential retrograde transport to the Cl was demonstrated, such that in the cat the ipsilateral dorsal Cl was shown to be the principal rogin of claustroproreate projections. In the baboon, the whole Cl projects onto area 8, while only the posteroventral part of the nucleus sends efferents to the visual cortes. The projection to the motor and premotor areas is present, but does not seem to be “essential.”

3. Discussion of the physiological literature, togetehr with anatomical evidence of reciprocal cortico‐claustral projections to closely similar regions of the Cl lead to the suggestion that the Cl is concerned with the integration of messages subserving visually‐directed movements. Some other functional implications are also discussed.
Projections of auditory cortex upon the thalamus and Midbrain in the owl monkey
Authors: Fitzpatrick Kathleen A. , Imig Thomas J.
Published: January 2005

Two tonotopically organized cortical fields, the primary (AI) and the rostral (R) fields, comprise the core of auditory cortex in the owl monkey. Injections of tritiated proline were made into each of these fields to determine their efferent projections using autoradiographic methods. Both AI and R project to the principal and magnocellular divisions of the medial geniculate body. In addition, R projects to the posterior part of the dorsal division of the medial geniculate. AI sends axons to the dorsomedial region and laminated portion of the central nucleus of the inferior colliculus. Labeling in the central nucleus following AI injections appears as a band of silver grains oriented parallel to isofrequency contours. Axons from R terminate in the dorsomedial region of the central nucleus of the inferior colliculus and in the ppericentral and external nuclei of the inferior colliculus. In addition, the rostral field projects to a small area of the medial pulvinar just anterior to the brachium of the superior colliculus.
A contribution to the electron microscopic morphometric analysis of peripheral nerve
Authors: Bronson Roderick T. , Bishop Yvonne , Hedley‐Whyte E. Tessa
Published: January 2005

Several aspects of data collection and analyses of peripheral nerve experiments employing light and electron microscopic morphometric techniques have not been adequately discussed in the literature. From statistical tests performed on nerve data, it was found that light compared with electron microscopic morphometry underestimates the number of small fibers. An optimum sampling strategy must take into account a potential bias toward small fibers introduced by measuring fibers from electronmicrographs. It must also take into account a potential bias introduced by the non‐random distribution of nerve fibers of different sizes in nerves. These biases are offset by sampling a large enough number of fibers from large enough area electron micrographs. A method is presented for analysing peripheral nerve data using the nested analysis of variance. This requires first dividing the usual bimodal nerve fiber distribution into component normally distributed parts. The number of fibers in the two portions of a bimodal distribution must be considered in data analysis. Knowledge of the variances of parameters to be studied in any particular nerve is necessary for optimum sampling strategies.
The representation of the body surface in somatosensory area I of the grey squirrel
Authors: Sur M. , Nelson R. J. , Kaas J. H.
Published: January 2005

Microelectrode mapping methods were used to determine the organization of primary somatosensory cortex, SmI, in grey squirrels. A systematic representation of the contralateral body surface was found within somatic koniocortex. This primary representation differs from maps of SmI in other mammals in at least two significant ways. The first way in which SmI of squirrels differs from the organization reproted for other mammals is that SmI of squirrels contains a double representation of the hand and parts of the forearm. The glabrous skin of the digits is represented twice in a mirror image fashion joined at the finger tips. The hairy skin of the digits, wrist, and parts of the forearm are also represented twice, once on each side of the joined representations of the glabrous skin. A second unique feature of SmI squirrels is that there is a small region of cortex completely surrounded by SmI that was unresponsive to light cutaneous stimuli under our recording conditions. This unresponsive zone is easily identified in brain sections by architectonic features that deviate from sensory koniocortex and approach motor cortex. A third significant finding was that the back is rostral to the belly in the representation of the trunk in SmI of squirrels. This is the reverse of the orientation reported elsewhere for SmI of mammals, but corresponds to the orientation of the trunk representation in Area 3b of owl monkey (Kaas et al., '76; Merzenich et al., '78). This similarity supports and earlier contention that the representation of the body in Area 3b of primates is the homolog of SmI in other mammals (Merzenich et al., '78).
The optic nerve of the brush‐tailed possum, Trichosurus vulpecula: Fibre diameter spectrum and conduction latency groups
Authors: Freeman Brian , Watson Charles R. R.
Published: January 2005

The principal findings of this report on the morphology and electrophysiology of the possum optic nerve are:

There are about 230,000 fibres in the optic nerve. This fibre count, based on electron microscopy, is slightly less than a previously reported estimate of the total number of ganglion cells in the possum retina.

The majority (> 98%) of the fibres of the optic nerve are myelinated axons of retinal ganglion cells. The diameters of these fibres range from 0.4–4.6 μm (axon diameter range: 0.3–3.8 μm) and the frequency distribution of the fibre diameters (and axon diameters) is positively skewed and unimodal.

The antidromic compound action potential of the possum optic nerve shows four negative peaks following stimulation of the optic chiasm. These peaks are associated with four conduction latency groups of fibres which have been designated t1, t2, t3 and t4 in order of increasing conduction latency.

The mean peak conduction velocities of the fibres in the conduction latency groups are 13.1 ms−1 (t1), 8.1 ms−1 (t2), 5.7 ms−1 (t3) and 3.1 ms−1 (t4).

There is no direct correlation between the frequency distribution of fibre (or axon) diameters as measured by electron microscopy of transverse sections of fixed optic nerve and the conduction latency groups.

The reconstruction of the possum optic nerve compound action potential on the basis of either axon or fibre diameter frequency distribution does not provide an acceptable, indirect correlation between the morphology and the electrophysiology of this optic nerve.
Electron microscopic analysis of postnatal histogenesis in the cerebellar cortex of staggerer mutant mice
Authors: Landis Dennis M. D. , Sidman Richard L.
Published: January 2005

Postnatal development of the cerebellar cortex has been compared in staggerer mutant and unaffected littermate mice. From postnatal day 3 to about day 21 the external granular layer in staggerer mice is decreased in thickness and area, and the number of postmitotic granule cell neurons is reduced. Those granule cells that are generated seem to differentiate normally, with the remarkable exception that they from only primitive junctions with Purkinje cell dendritic shafts. These specialized junctions are not superseded by the normal parallel fiber: Purkinje spine synapses and disappear by the third week. Purkinje cell somata and dendrites are smaller than normal at all stages examined. The dendrites are not confined to the sagittal plane as in the normal and, unique among mutant or other animals described to date, they exhibit virtually no branchlet spines. All other cortical synaptic relations of granule and Purkinje cells, including climbing fiber: Purkinje spine synapses, appear qualitatively normal. However, by 28 days virtually all staggerer granule cells have degenerated. While the primary genetic defect remains unknown, we postulate that the morphological abnormalities may be attributable to a block in the normal developmental relationship between granule cells and Purkinje cells. The small cell size and failure to form branchlet spines suggest that the Purkinje cell abnormality may be closer to the primary effect of the mutant gene than the more flagrant hypoplasia and degeneration of granule cell neurons.
Electron microscopic demonstration of a supraependymal cluster of neuronal cells and processes in the hamster third ventricle
Authors: Card J. P. , Mitchell Jerald A.
Published: January 2005

A supraependymal cluster of neuronal cells and processes consistently present on the floor of the hamster third ventricle was identified and characterized by means of correlative scanning (SEM) and transmission (TEM) electron microscopy. SEM revealed each cluster to be ovoid with the majority of its surface covered by dome‐shaped protrusions and fine beaded fibers. A number of processes traveling individually or in groups also entered or exited from the cluster at its base. As these processes passed over the ventricular surface, they contributed to an extensive network on the floor and ventral aspect of the ventricular wall. Some processes terminated on the ependymal surface in bulbous endings while others penetrated the ependyma. The neuronal nature of these clusters and their associated processes was confirmed at the TEM level. The dome‐shaped protrusions visible on the surface of the cluster in SEM corresponded to apical surfaces of neurons confined to the peripheral aspect of a core of loosely arranged processes. These cells exhibited a prominent nucleolus, stacks of rough endoplasmic reticulum (RER), polyribosomes, Golgi cisternae, mitochondria and microtubules (MT) and gave rise to dendritic processes which extended into the core. These dendrites gave off branches at acute angles and contained polyribosomes, single cisternae of RER and evenly spaced MT. Other profiles of processes within the core shared these characteristics, suggesting that they also were branches of the peripheral cells. Axons present within the core and on the cluster's surface exhibited vesicle‐filled varicosities which frquently established synaptic contact with the peripheral cells and their processes. The presence of an intraventricular cluster of neurons which potentially communicates with centers extrinsic to the ventricle may have important implications in the hypothesized role of cerebrospinal fluid and tanycytic ependyma in the neuroendocrine regulation of anterior pituitary function.