bluuebunny/crossref_metadata_2025 huggingface dataset:
Electron microscopic features and proliferation of astrocytes in the corpus callosum of the rat
Authors: Mori S. , Leblond C. P.
Published: December 2004

The gold chloride sublimate method of Ramón y Cajal was used to stain astrocytes in the corpus callosum of 60–80 g male rats. The opacity of the metal‐stained astrocytes to the electron beam allowed their study in the electron microscope. It was thus found that metal deposits are absent from the nucleus but are present over two cytoplasmic structures: bundles of filaments and dense bodies.

Once the features of astrocytes had been observed in metal stained preparations, it became possible to identify them in sections stained for electron microscopy by the routine uranyl‐lead sequence. The presence of filament bundles in the cytoplasm was the most useful diagnostic feature. Dense bodies also helped. The nucleus was relatively large and light with a very distinct, often irregular nuclear envelope. The rather light cytoplasm contained glycogen granules, with few ribosomes and cisterns of endoplasmic reticulusm. However, a few otherwise typical astrocytes had fairly dark nucleus and cytoplasm.

After gaining experience with the electron microscope, it was possible to identify most astrocytes in the light microscope by their nuclear features. Counts of the frequency of astrocytes using either the light or electron microscope revealed that they make up about one quarter of the glial population of the corpus callosum.

The main properties of astrocytes seemed to be: (1) plasticity of the cell surface, which infiltrates all available spaces around it; (2) apparent rigidity of the bundles of filaments present in the processes, where they may play a supporting role; and (3) ability of astrocytes to undergo division, as demonstrated both by the uptake of 3H‐thymidine into 1.7% of these cells and by the presence of mitotic figures.
Identification of preganglionic parasympathetic neurons in the sacral spinal cord of the cat
Authors: Oliver John E. , Bradley William E. , Fletcher Thomas F.
Published: December 2004

The preganglionic parasympathetic neurons in the sacral spinal cord of the cat have been demonstrated by retrogade changes following section of the pelvic nerve.

Transection of the pelvic nerve twice, a week apart, was necessary to produce reliable signs of chromatolysis in the preganglionic neurons. Serial sections of the sacral spinal cord were made and the location of affected cells plotted.

The sacral parasympathetic nucleus was located in the intermediate region of S‐2 and S‐3. The majority of the perikarya were located in the intermediolateral cell column, but a significant number were also found in the intermediomedial column.

The distribution of afferent fibers in the pelvic nerve was demonstrated by chromatolysis in cells of the dorsal root ganglia. Retrograde changes were limited to the ganglia of S‐2 and S‐3 in five cats, while a few cells with chromatolysis were found also in the S‐1 ganglion of four cats.
Autoradiographic and histological studies of postnatal neurogenesis. IV. Cell proliferation and migration in the anterior forebrain, with special reference to persisting neurogenesis in the olfactory bulb
Authors: Altman Joseph
Published: December 2004

The properties and fate of the cells of the subependymal layer of the anterior lateral ventricle and its rostral extension into the olfactory bulb were examined. In one experiment, histological analysis was made of this structure in a large group of rats, ranging in age from newborn to adults. It was established that the ventricular subependymal layer and its rostral extension are present as proliferative and migratory matrices throughout the period studied, with relatively little reduction in size from birth to adulthood. In another, autoradiographic study, the proliferation and migration of cells of this system, and their destination and mode of differentiation, were studied in rats that were injected with thymidine‐H3 at 30 days of age and killed at intervals ranging from 1 hour to 180 days. There was a declining gradient in cell proliferation in a caudorostral direction from a high level near the lateral ventricle to the absence of cell proliferation in the olfactory bulb. The labeled cells that were present in high proportion near the lateral ventricle in the rats killed 1–24 hours after injection had further multiplied and moved to the middle portion of the “rostral migratory stream” by the third day, and were located in the subependymal layer of the olfactory bulb by the sixth day after injection. By the twentieth day the labeled cells disappeared from the subependymal layer of the olfactory bulb and were distributed throughout the internal granular layer. The differentiated cells were tentatively identified as granular nerve cells and neuroglia cells. These results established that the major target structure of cell production in the subependymal layer of the lateral ventricle in young‐adult rats is the olfactory bulb, with only moderate contribution made to the anterior neocortex and basal ganglia. It was postulated that the function of cell migration to the olfactory bulb is the renewal of its cell population.
The structure of the terminal ganglionic mass of the locust, Schistocera gregaria (forskäl)
Authors: Seabrook W. D.
Published: December 2004

Sections of the terminal ganglionic mass reveal a neuropile comprising four fused units corresponding to the eighth, ninth, tenth, and eleventh abdominal ganglia. Segmentally arranged groups of interneurons further illustrated the segmental nature of this ganglionic mass. Condensation of the component ganglia has resulted in a reduction in the number of commissures, the eighth ganglion retaining five of the original eight found in a simple ganglion, and each subsequent ganglion retaining four. There is a reduction in the number of discrete neuron groups and in the number of lateral interneurons coincident with the degree of condensation. Associated with the degree of condensation is a relocation of the motor neurons from the lateral ventral regions of the ganglion to the dorsal surface. One‐hundred‐five neurons have been traced within the terminal ganglionic mass.
Distribution of hippocampal mossy fibers in the rat. An experimental study with silver impregnation methods
Authors: Blackstad T. W. , Brink K. , Hem J. , June B.
Published: December 2004

The paper deals with the distribution of the axons that arise in the fascia dentata and go to the hippocampus proper. lesions were placed in the fascia dentata and degenerating mossy fibers were mapped by silver impregnation, mostly according to the method of Fink and Heimer ('67). The fascia dentata and the layer of mossy fibers in the rat form a curved and twisted structure extending from the level of the posterior aspect of the septum to the temporal tip. The horizontal serial sections used for this study were, therefore, in part interpreted by means of three‐dimensional reconstructions.

Mossy fibers do not enter the fimbria at any point. Degenerating fibers can be traced to the limit between regio superior (CA 1) and regio inferior. This dentato‐hippocampal connection displays a pattern of precise localization, each level of fascia dentata projecting onto a restricted level of regio inferior. The bands of degenerated mossy fibers produced by lesions in the fascia dentata were largely oriented in the transverse direction (slightly in a temporal direction) and were somewhat wider distally than at the origin from the hilus. Very narrow bands were seen in a few animals with particularly small lesions.
The distribution of recurrent purkinje collateral synapses in the mouse cerebellar cortex: An electron microscopic study
Authors: Larramendi L. M. H. , Lemkey‐Johnston N.
Published: December 2004

Myelinated fibers found in the lower molecular layer of the mouse cerebellum form synaptic enlargements of a uniform morphological appearance. Similar synapses have been observed to come from myelinated fibers in the upper granularlower Purkinje cell layer. Both have been interpreted as Purkinje collateral boutons. The study of the distribution of Purkinje collateral synapses revealed that one third formed the supraganglionic plexus in the lower molecular layer and two thirds formed an infraganglionic plexus in the lower Purkinje upper granular zone. In the molecular layer, basket cell somata and dendrites received the gratest number of Purkinje collaterals, while Purkinje dendrites and branchlets received relatively few. In the infraganglionic plexus, the Purkinje collaterals terminated on “very low basket” cells and upon a dense dendritic “thicket” belived to be contributed largely by basket cells.
Electron microscopic identification of three classes of oligodendrocytes and a preliminary study of their proliferative activity in the corpus callosum of young rats
Authors: Mori S. , Leblond C. P.
Published: December 2004

In recent electron microscope studies of the corpus callosum in 60–80 gm male rats, some of the cells were identified as microglia by staining with the weak silver carbonate method of del Rio‐Hortega, and others as astrocytes by staining with the gold chloride sublimate method of Ramón y Cajal. In the present work, the cells which did not belong in one of these two groups were examined in the light microscope using semithin sections stained with toluidine blue and in the electron microscope using thin sections stained with uranyl‐lead.

These cells make up a large, somewhat heterogeneous group, but they have a few common features: regular nucleus, cytoplasm rich in ribosomes and microtubules, and a variable number of narrow, non‐branching fine processes of uniform diameter. Because of these features, the cells are all taken to be oligodendrocytes.

Three classes may be described within this group of cells: (a) light oligodendrocytes, which are large cells with pale nucleus, a large nucleolus, a cytoplasm containing rather small organelles as well as many free ribosomes, and giving off numerous fine processes; they make up about 6% of the glial cells in the corpus callosum; and they undergo mitosis at a rapid rate; (b) medium‐shade oligodendrocytes, which are somewhat smaller cells with moderately dense nucleus and cytoplasm, containing well developed organelles, and giving off a fair number of fine processes; they make up about a quarter of the glial cells; and they undergo mitosis at a moderate rate; (c) dark oligodendrocytes, which are even smaller cells with very dense nucleus and cytoplasm, containing a prominent Golgi and structures referred to as lamellar bodies, and giving off very few fine processes; these cells make up about 40% of the glial cells; they do not undergo mitosis and probably arise from divisions of medium oligodendrocytes.
An experimental silver study of the ascending projections of the central gray substance and adjacent tegmentum in the rat with observations in the cat
Authors: Chi Carl Chungming
Published: December 2004

The ascending projections of the central gray substance and adjacent tegmentum in the rat and cat were studied with the Fink‐Heimer (1967) modification of the Nauta method. Following lesions of the circumaqueductal gray, degeneration was traced along the dorsal longitudinal fasciculus of Schütz, a reciprocal association pathway between the central gray and the hypothalamus, into the dorsal and posterior hypothalamus, midline and intralaminar regions of the thalamus, and the zona incerta of the subthalamus. Another group of fibers travelled ventrally from the central grey to reach the ventral tegmental area of Tsai; some of these fibers continued rostrally to terminate in the lateral hypothalamus. Other fibers distributed to the midbrain tegmentum as components of Weisschedel's radiatio grisea tegmenti. Lesions which extended into the adjacent tegmentum produced a larger quantity of degeneration than did lesions confined to the central gray, but the patterns of degeneration were similar in both cases. The ascending projections of the central gray in the rat and cat were found to have similar distributions but were slightly more massive in the cat.

No evidence of fiber degeneration was detected in the ventromedial hypothalamus. Negative results, however, must be interpreted with caution, for they may be due to an excessively small caliber of axons and/or peculiar modes of axon termination in hypothalamic tissue.
Telencephalic projections of the nucleus rotundus in the pigeon (Columba livia)
Authors: Karten Harvey J. , Hodos William
Published: December 2004

The nucleus rotundus receives a massive ascending projection from the optic tectum. Stereotaxic lesions were placed in the nucleus rotundus and its efferent projections studied by means of the Nauta‐Gygax and Fink‐Heimer methods for degenerating axons and terminals. Efferent rotundal axons form the lateral part of the fasciculus prosencephali lateralis (FPL), pass through the lateral portion of the paleostriatum primitivum (PP) and augmentatum (PA) and enter the overlying ectostriatum.

The ectostriatum was found to consist of at least two distinct cytologic regions: a central core (E) containing larger and more scattered cells and a peripheral belt with smaller, more densely packed neurons (Ep). Rotundal efferents terminate on the full extent of the central core of larger neurons. No evidence was found of any significant projection to the overlying periectostriatal belt or to the surrounding neostriatum. All portions of the central core of the ectostriatum receive projections from the nucleus rotundus. This projection is topologically organized on a rostro‐caudal axis relative to the nucleus rotundus. There was no indication of the existence of inter‐rotundal, rotundo‐tectal or rotundus to contralateral ectostriatal projections.

These findings demonstrate the existence of a massive ascending visual pathway to the telencephalon, arising from the optic tectum and terminating in a cytologically distinct projection field within the telencephalon. The relationship of this pathway to known visual pathways in mammals and reptiles is discussed.
Photically evoked unit activity in the tectum opticum of the squirrel monkey
Authors: Kadoya Satoru , Wolin Lee R. , Massopust Leo C.
Published: December 2004

Visually evoked unit responses of the tectum were studied in the squirrel monkey. The results showed that the superior colliculus had a definite functional laminar organization. Units responding to diffuse light were found in the upper part of the stratum griseum superficiale, units having antagonistically segregated receptive fields in the middle portion, and units sensitive to moving objects in the lower portion as well as in the stratum opticum. Retinotopic projection was also observed. The pretectal region contained mainly “tonic‐on” and “inhibitory” units. No specific localization was observed in the distribution of these units.
The distribution of neurofibrils coextensive with microtubules and neurofilaments in dendrites and axons of the tectum, cerebellum, and pallium of the frog
Authors: Potter H. D.
Published: December 2004

Correlation of electron micrographs with the results of a variety of reduced silver stains for light microscopy indicates that neurofibrils may be stained in locations where either neurofilaments or microtubules predominate, depending upon the procedure. Reduced silver techniques following fixation with alcohol or aldehyde solutions (Cajal's block method II, methods of Nonidez, Bartelmez, DeCastro, Bodian, Guillery, and Holmes) stain neurofibrils coextensively with neurofilaments (fnf) in myelinated axons, large dendrites, and synaptic boutons but do not stain neurofibrils in most radial dendrites of the tectum or parallel fibers of the cerebellum, where numerous microtubules but few neurofilaments are present. In the latter locations neurofibrils (tnf) are stained following primary fixation in silver nitrate alone (Cajal's block method I) or alcoholic silver nitrate (method Ic), with gold toning of the sections. The methods staining tnf are highly successful in showing the distribution and orientation of the parallel fibers and radial dendrites as well as other thin axons and dendrites in the grey matter including the archipallium. Even in regions containing fnf in numerous processes, it is clear that the majority of fibers in the adult frog brain contain only tnf.
Terminal degeneration and glial reactions in the lateral geniculate nucleus of the squirrel monkey after eye removal
Authors: Wong‐Riley Margaret T. T.
Published: December 2004

Young adult squirrel monkeys were subjected to unilateral or bilateral enucleation, and allowed to survive for varying periods of time. Transneuronal degeneration confirms previous studies that the homogeneous parvocellular mass actually has four hidden laminae. Electron microscopic studies show that the retinal (RL) terminals undergo three stages of degenerative changes after enucleation: neurofilamentous hyperplasia; increased electron density; and phagocytosis by glial elements. The time course of these changes is correlated with those of the Glees and the Nauta preparations. The other types of axons remain normal. Three types of neuroglial cells are found in the normal and degenerating LGN: Oligodendrocytes, astrocytes and a phagocytic glial cell type. The oligodendrocytes do not appear to participate actively in phagocytosis. The astrocytes undergo a filamentous hyperplasia during degeneration; they may engulf some degenerating terminals, and contribute to the formation of gliosis. The phagocytic glial cells proliferate during the degenerative process, and actively phagocytose both the dense terminals and the degenerating myelinated axons.
Nigrostriatal and nigrothalamic fibers in the rhesus monkey
Authors: Carpenter Malcolm B. , Peter Philip
Published: December 2004

Lesions in caudal parts of the substantia nigra (SN) produced in 11 monkeys were localized to lateral, medial and central regions. Resulting degeneration was studied by the Wiitanen technic in transverse and sagittal sections. Ascending nigral efferents project into Forel's field H where they divide into medial and lateral bundles. Fibers of the medial bundle terminate in portions of the ventral lateral (VLm) and ventral anterior (VAmc) thalamic nuclei. Quantitatively larger numbers of fibers project laterally dorsal to, and within, the subthalamic nucleus. These nigral efferents traverse the internal capsule and globus pallidus to enter the putamen (P) and parts of the caudate nucleus (CN). Nigral efferent fibers in the globus pallidus appeared entirely en passage. The location of degeneration in the putamen appeared related to the part of the SN destroyed. An apparent correspondence exists between: (1) lateral parts of SN and dorsal regions of P, and (2) medial parts of SN and ventral regions of P.

The pars reticularis of SN gives rise to nigrothalamic fibers while nigrostriatal fibers arise from the pars compacta. Data suggest that reciprocal topographic relationships may exist between nigrostriatal and strionigral projections and that these fibers appear to form a closed feedback loop concerned with dopamine transport. Lesions in SN concomitantly interrupt large numbers of corticotegmental and corticothalamic fibers.
The termination of retinal axons in the pretectal region of mammals
Authors: Scalia Frank
Published: December 2004

The retinopretectal projection was investigated in the rat, mouse, rabbit and tree shrew primarily by means of the Fink‐Heimer technique. The experimental animals survived for varying periods of time following unilateral eye removal. The retinopretectal projection in each species was predominantly contralateral. A dense field of terminal degeneration was observed in the nucleus of the optic tract and in the olivary pretectal nucleus in each of the species. A less dense projection was observed for the posterior pretectal nucleus in each species. A sparse projection to the anterior pretectal nucleus was observed in the rabbit and tree shrew but not in the rat or mouse. A dense, ipsilateral projection to the olivary pretectal nucleus was observed in the rat, mouse and tree shrew. A sparse, ipsilateral projection was found in the anterior end of the posterior pretectal nucleus in the rat, mouse and tree shrew and in the posterior part of this nucleus in the rabbit. In the tree shrew, a small amount of terminal degeneration was found in the ipsilateral anterior pretectal nucleus. The nomenclature used here is uniformly applicable among the species described.
Retinal projections in the perch‐like teleost Eugerres plumieri
Authors: Vanegas Horacio , Ebbesson Sven O. E.
Published: December 2004

Anatomical studies on the organization of the visual system of Eugeres plumieri have been initiated with an analysis of the distribution of retinal fibers in the brain. Twelve adult specimens were unilaterally enucleated. After postoperative survival periods ranging from six to 30 days, the fishes were perfused and the brains processed according to several modifications of the Nauta technique for the demonstration of degenerating axons and terminals (Ebbesson, '70). Although some terminal degeneration can be seen as early as six days, the degenerating fibers and terminals are best demonstrated in specimens with post‐operative survivals of 15 days or longer.

The optic tract is entirely crossed and issues fascicles to the hypothalamus, nucleus geniculatus lateralis, nucleus opticus dorsolateralis thalami, nuclei pretectales, nucleus corticalis, and tectum opticum. The nucleus geniculatus lateralis is unusually large and well laminated, as is the optic tectum. The retinal input to the latter is distributed to, and terminates in, the stratum opticum and the highly differentiated stratum griseum et fibrosum superficiale. Debris of degeneration was also consistently seen in the stratum album centrale.
Patterns of cell and fiber distribution in the neocortex of the reeler mutant mouse
Authors: Caviness V. S.
Published: December 2004

In the neocortex of the reeler mutant mouse, there is inversion in the normal relative positions of polymorphic and pyramidal cells and of large with respect to medium‐sized and small pyramidal cells. Granule cells are concentrated at a near‐normal mid‐cortical level in the mutant. As in the normal animal, and despite cell malposition in reeler, the principal tangential fiber system lies in the zone of polymorphic cells. Large fiber fascicles, known from experimental studies to be principally thalamo‐cortical afferents, enter the tangential fiber system in the polymorphic cell zone of both reeler and normal neocortex. In the mutant these fascicles must traverse the full width of the cortex to reach this fiber system in its superficial location. In both normal and mutant animals single fibers, again principally thalamo‐cortical afferents, pass from the principal tangential fiber system to ramify in a fiber feltwork in the zone of granule cells. In the mutant these descend whereas in the normal animal they ascend. Also, as in the normal mouse, single fibers pass radially between all levels of the mutant cortex and the central white matter. Regional variations in the character, the pattern of distribution and the relative prominence of homologous cell and fiber elements are closely parallel in reeler and normal. This suggests that cell differentiation and the tangential organization of reeler neocortex are normal despite cell malposition in the mutant.
Histochemical evidence of altered development of cholinergic fibers in the rat dentate gyrus following lesions: I. Time course after complete unilateral entorhinal lesion at various ages
Authors: Nadler J. Victor , Cotman Carl W. , Lynch Gary S.
Published: December 2004

The entorhinal cortex of rats was removed at various times during development, and the reaction of the cholinergic septohippocampal input to the dentate gyrus was examined by use of acetylcholinesterase histochemistry. When the ipsilateral entorhinal cortex is completely removed, the outer 70‐75% of the molecular layer of the dentate gyrus is almost completely denervated. After such a lesion at 5 to 33 days of age, the acetylcholinesterase staining initially intensified throughout the denervated area, indicating that the septohippocampal fibers branched or elongated. This reaction could be detected within one day after a lesion at 11 days of age and within three or five days after lesions at earlier or later times. Whereas the initial response of the septohippocampal fibers was independent of the age at which the lesion was made, their final localization depended on the developmental state of the animal. After lesions at the age of 5 or 11 days, the reactive septohippocampal fibers became restrictd to the outer one‐sixth to one‐third of the molecular layer within two days after appearance of their initial reaction. A similar concentration of reactive fibers was demonstrable after lesions at 16, 18 or 21 days of age, but some reaction persisted in the middle third of the molecular layer. Finally, after lesions at 26 or 33 days of age the proliferating cholinergic fibers ultimately were uniformly distributed throughout the outer 60% of the molecular layer.

These results suggest that septohippocampal fibers initially extend or sprout throughout the denervated area to replace the lost perforant path fibers. However, the reactive fiber population becomes restricted to the outer edge of the molecular layer if the entorhinal lesion is made before the period of cholinergic synaptogenesis and concentrates in this same zone if it is made while cholinergic synapses are forming. We suggest that either the proliferative reaction continues in the outer part of the molecular layer and subsides in other parts of the denervated area or septohippocampal fibers move outward through the molecular layer to assume a more superficial location.

After entorhinal lesions at 16 days of age or later the pale‐staining zone (containing fibers that originate in hippocampus regio inferior) immediately deep to the denervated area widened. If the lesion was made earlier, this zone never developed at most septotemporal levels of the dentate gyrus. These results are probably related to the extension of regio inferior fibers into the denervated area.
Cat cones have rod input: A comparison of the response properties of cones and horizontal cell bodies in the retina of the cat
Authors: Nelson Ralph
Published: December 2004

The responses of horizontal cell bodies and cones in the retina of the cat have been studied by means of intracellular recording and Procion dye injection In an isolated, arterially perfused eyecup preparation. Comparison of the hyperpolarizing responses of these units to red and blue stimuli of different intensities indicated that all morphological varieties of horizontal cells and, additionally, cones themselves, had mixed rod and cone input. The rod input into horizontal cell bodies is thus explained on the basis of cone physiology. The half‐saturating intensity of 441 nm stimuli for the rod input into cones and horizontal cells was about 400 quanta/μm2/sec and about 160,000 quanta/μm2/sec for the cone input. Little of this difference can be related to the different quantum catching abilities of rods and cones. The spatial properties of horizontal cell bodies and cones have been characterized using stimuli consisting of long slits in conjunction with a continuous cable model. Space constants for horizontal cells ranged from 210 μm to 410pm, whereas those for cones ranged from 50μm, or possibly less, to 180 μm. It is argued that horizontal cell bodies of the cat retina form electrical networks, and that the sizes of the receptive fields generated in these networks may be limited by the diameters of the primary and secondary dendrites of horizontal cells. The rod and cone fields of horizontal cell bodies were found to be nearly coextensive in space, arguing against the notion that substantial rod input came from distant, rod‐dominated terminal arborizations.
The locust wing hinge stretch receptors. II. Variation, alternative pathways and “mistakes” in the central arborizations
Authors: Altman J. S. , Tyrer N. M.
Published: December 2004

The central arborizations of the stretch receptor (SR) neurones are very consistent from one individual to another. Superimposition of normalized neurones from eight individuals of Locusta show very little variation even in the detailed branching pattern. There is, however, a commonly found alternative course for the main medial branch in the metathoracic ganglion. Rare, radical departures from the normal branching pattern are termed “mistakes.” Only three have been found, all in the forewing SR projection, one with an extra branch and two with missing branches.

Terminals of twigs in the alternative region of the medial branch occupy consistent positions in the neuropile, although these are reached by different routes. Mistakes have terminals in areas normally containing SR endings. Both these findings suggest that there may be labelled sites in the neuropile which the growing tips of the SR neurones seek out.
Specific neuroanatomical changes in chemosensory mutants of the nematode Caenorhabditis elegans
Authors: Lewis James A. , Hodgkin Jonathan A.
Published: December 2004

Eight of nineteen chemotactic mutants of the nematode Caenorhabditis elegans have morphological defects in the sensory endings of neurons at the tip of the head. The mutants were obtained as worms swimming away from attractant or found amongst male potency mutants or mutants exhibiting erratic behavior. The nineteen mutants fall into at least twelve complementation groups. Mutants E1034 and E1035, alleles of che‐1, show morphological alterations in the sensory endings of amphidial neurons and inner labial type 2 neurons, both prospective chemosensory neurons. Both mutants contain noncomplementing ts sterile mutations linked to the chemosensory mutation. E1066 shows abnormalities in all the sheath cells associated with the sensory neurons and in the bundling pattern of the amphidial neurons. El 126 is structurally abnormal only in the sensory endings of inner labial type 2 neurons, supporting a chemosensory role for these neurons. E1033 (cke‐2) and El 124 (cke‐3) cause defects in the ciliary structure of all but one type of ciliated sensory neuron in the head. E1062 is grossly defective in head structure and the structure of the male copulatory organ, suggesting these opposite ends of the nematode rich in sensory structures share gene functions in embryogenesis. Our study illustrates the possibilities for genetic dissection of the development of a small set of nerves in a simple organism.
Projections from the amygdaloid complex and adjacent olfactory structures to the entorhinal cortex and to the subiculum in the rat and cat
Authors: Krettek J. E. , Price J. L.
Published: December 2004

Axonal projections are described from the lateral and hasolateral nuclei of the amygdaloid complex, and from the overlying periamygdaloid and pre‐piriform cortices and the endopiriform nucleus, to the lateral entorhinal area, the ventral part of the subiculum, and the parasubiculum in the cat and rat. All of these projections have well‐defined laminar patterns of termination, which are complementary to those of other projections to the same structure.

Based on these results, and on cytoarchitectonic distinctions, the lateral entorhinal area has been divided into dorsal, ventral, and ventromedial subdivisions. The olfactory bulb and prepiriform cortex project to layers IA and IB, respectively, of all three subdivisions, but the lateral amygdaloid nucleus has a restricted projection to layer 111 of the ventral subdivision only. The periamygdaloid cortex projects to layer II of the ventromedial and adjoining parts of the ventral subdivisions.

The ventral part of the subiculum receives fibers from the posterior division of the hasolateral nucleus, which terminate in the cellular layer and the deep half to one‐third of the plexiform layer. The periamygdaloid cortex and the endopiriform nucleus also project to the same part of the subiculum, but these fibers terminate in the outer part of the plexiform layer. None of these projections extend into the dorsal part of the subiculum.

The posterior division of the basolateral nucleus also projects to the posterodorsal part of the parasubiculum (“parasubiculum a” of Blackstad, 1956). These fibers end in the deeper part of the plexiform layer and the superficial part of the cellular layer.
Afferent connections of the habenular nuclei in the rat. A horseradish peroxidase study, with a note on the fiber‐of‐passage problem
Authors: Herkenham Miles , Nauta Walle J. H.
Published: December 2004

The afferent connections of the habenular complex in the rat were examined by injecting horseradish peroxidase (HRP) into discrete portions of the habenular nuclei by microelectrophoresis.

1. HRP deposits confined to the lateral half of the lateral habenular nucleus labeled a multitude of cells in the entopeduncular nucleus. Numerous labeled cells also appeared in such cases in the lateral hypothalamus, indicating that the lateral habenular nucleus is a major convergence point of projections from these otherwise.

2. HRP injected into the medial part of the lateral habenular nucleus labeled cells in the same regions, but more in the diagonal band and fewer in the entopeduncular nucleus than were labeled by more lateral injections. The contrast suggests that the projections from the basal forebrain and entopeduncular nucleus to the lateral habenular nucleus are somewhat topographically organized.

3. Injections of the medial habenular nucleus labeled an abundance of cells in the posterior parts of the supracommissural septum, but also a small number of cells in the diagonal band and mesencephalic raphe.

4. HRP injected into the stria medullaris labeled cells in all of the afore‐mentioned areas and, in addition, cells in several olfactory structures, confirming that HRP may be taken up by fibers of passage and label their cells of origin, and suggesting that olfactory structures contribute fibers to the stria medullaris that do not terminate in the habenula.
Cerebellar histogenesis in the lurcher (Lc) mutant mouse
Authors: Swisher Dorothy A. , Wilson Doris B.
Published: December 2004

The postnatal development of the cerebellar cortex of normal and lurcher (Lc) mutant mice was studied by neurohistological and autoradiographic techniques at ages ranging from 2 days through 18 days after birth. Lurcher shows severe defects in the granule cells and Purkinje cells soon after birth.

A decrease in the generative layers of the external granular layer is soon as early as two days in the lobulus simplex and by six days of age in the uvula. Granule cell death is common before and during granule cell migration, from 2 to 18 days of age. Loss of granule cells is reflected in reduced growth of the molecular and granular layers. Purkinje cell abnormalities appear at three to four days after birth in the form of crowding, failure of nuclear growth, and condensed or lessened cytoplasm. Purkinje cell death is apparent at four to six days of age depending on the region of the cerebellum.
Anatomy of the retina of the mink (Mustela vison)
Authors: Dubin Mark Wm. , Turner Linda
Published: December 2004

The retina of the normal pigmented mink has been studied by light and electron microscopy. This retina resembles the typical vertebrate retina in its pastterns of lamination and synaptic interconnectivity. Rod and cone outer segments and receptor spherule and pedicle endings are found. At least two different types of horizontal cell processes are seen with the electron microscope, suggestive of rabbit A and B types. Ribbon and conventional synapses are found in both plexiform layers; conventional synapes are also present in the inner nuclear layer. Quantitative studies of the inner plexiform layer revealed amacrine:bipolar synapse ratios (3.3:1) similar to those of the cat and monkey. Other quantitative parameters also resembled those previously reported for species with retinas that predominantly contain concentric‐type receptive fields.
The organization of the pulvinar in the grey squirrel (Sciurus carolinensis). I. Cytoarchitecture and connections
Authors: Robson J. A. , Hall W. C.
Published: December 2004

The posterior neocortex in the gray squirrel, Sciurus carolinensis, includes an extensive region which receives projections from the pulvinar. Previous studies have demonstrated that this cortical region can be subdivided on the basis of differences in cytoarchitecture and electrophysiologically defined representations of the visual field. The main purpose of the present paper was to determine whether these cortical subdivisions could be related to corresponding subdivisions in the pulvinar. The methods used to trace connections included anterograde degeneration, anterograde axonal transport of tritiated amino acids and the retrograde axonal transport of horseradish peroxidase. The results indicate that the pulvinar in this species contains at least three main subdivisions which can be distinguished by their cytoarchitecture and their patterns of connections. A caudal subdivision contains large, evenly‐spaced neurons and receives bilateral input from the superficial, retinal‐recipient layers of the superior colliculus. This caudal subdivision has reciprocal interconnections with a cytorchitectonically ditinct area in the temporal cortex. A rostro‐lateral subdivision contains smaller, more lightly stained neurons which tend to form cluster. This subdivision receives only ipsilateral tectal input and projects to occipital area 18. This subdivision does not receive input form areas 17, 18, and 19, or form the temporal cortex. Finally, a rostro‐medial subdivision is cytoarchitectonically similar to the rostro‐lateral subdivision but receives little, if any, input form the superior colliculus. This rostro‐medial area does, however, receive corticofugal projections form occipital areas 17, 18, and 19, and projects to area 19. These patterns of connections suggest that each of these subdivisions has close associations with the visual system. The question of whether similar subdivisions are present in the visual thalamus of other species is discussed.
Horizontal cells of the pigeon retina
Authors: Mariani Andrew P. , Leure‐DuPree Alphonse E.
Published: December 2004

Two types of horizontal cells are seen in Golgi‐impregnated retinas of the pigeon. Type I horizontal cells are compact, “brush‐shaped,” and have an axon ending as an irregular spinous arborization. The majority of the dendrites terminate in the distal part of the outer plexiform layer (OPL) as clusters which contact cones, but some terminate as single expansions in the proximal part of the OPL. The axon terminal spines are found only in the distal part of the OPL and contact both rods and cones. Pigeon Type I horizontal cells are Caja's “brush‐shaped” cells, and their axon terminals resemble Caja's “stellate” cells. Type II horizontal cells have irregular, wavy, multi‐branched dendrites, appear horizontally flattened, and lack axons. The dendrites terminate in the proximal part of the OPL as isolated spines and contact only cones. The Type II horizontal cells of the pigeon have not been previously described in the avian retina.
Cells of origin and terminal distribution of descending projections of the rat somatic sensory cortex
Authors: Wise S. P. , Jones E. G.
Published: December 2004

The retrograde, horseradish peroxidase technique has been used to demonstrate the cells of origin of corticofugal fiber systems arising in the rat somatic sensory cortex and projecting to the striatum, diencephalon, brainstem, and spinal cord. Correlative experiments conducted with the anterograde, autoradiographic method have been used to confirm the terminal distribution of many of these fiber systems. Corticofugal pathways directed to subcortical structures arise in the first and second somatic sensory areas exclusively from pyramidal cells of the infragranular layers, V and VI. Fibers which descend to the midbrain, pons, medulla and spinal cord arise exclusively from the largest pyramidal cells, the somata of which are found in the deep part of layer V (layer VB). There is some evidence for a sublaminar organization of the different classes of efferent cells within this layer. Fibers projecting to the diencephalon arise from somata situated throughout layer VI and to a lesser extent in layer V. Corticostriatal fibers arise only from cells with somata in layer V, but the somata are more superficially situated than those of the other classes of corticofugal neurons. The laminar distribution of the somata of corticofugal neurons differs considerably from that of commissural and ipsilateral corticocortical neurons.
Differential effects of monocular deprivation seen in different layers of the lateral geniculate nucleus
Authors: Casagrande V. A. , Guillery R. W. , Harting J. K.
Published: December 2004

Recent investigations have suggested that the morphological effects of monocular deprivation can be explained by a developmental competitive interaction between the pathways from the two eyes. This study presents evidence in the tree shrew for binocular competition and for an unequal effect of such competition on the different layers of the lateral geniculate nucleus.

The effects of monocular deprivation were evaluated by comparing cell size changes in the binocular and monocular segments of the lateral geniculate nucleus in three tree shrews raised with one eye sutured. In two of these animals the open eye was injected with 3H proline in order to identify accurately geniculate layers innervated by the non‐deprived eye. Cell sizes in three normal animals and one monocularly enucleated animal were measured for comparison.

The results show the following main effects: First, that monocular deprivation significantly changes cell size in the binocular but not the monocular segment of the geniculate nucleus. Comparisons with cell size in normal animals indicates that non‐deprived cells may grow in response to deprivation. Second, that cell size in geniculate lamina 3 is not affected by monocular deprivation, suggesting that cells in this layer are morphologically or functionally secluded from competitive interactions affecting the other layers. Finally, that monocular enucleation in the adult tree shrew affects all parts of the geniculate nucleus including layer 3 and the monocular segment, demonstrating that these parts of the geniculate nucleus are responsive to lack of retinal innervation.
Anatomical and physiological localization of visual and infrared cell layers in tectum of pit vipers
Authors: Kass Leonard , Loop Michael S. , Hartline Peter H.
Published: December 2004

Visual and infrared cell layers were identified in the tectum of the pit vipers crotalus viridis and Sistrurus melitus. Histologic reconstructions of 48 lesions utilizing the Prussian Blue technique were correlated with micrometer depth readings for 251 visual, infrared and bimodal single unit recordings. The visual cell layer extends caudally from approximately the level of the habenula to the rostral border of the posterior corpora quadrigemina. Neurons responding to visual stimulation are generally contained within zones 7b‐13, i.e., the superficial 600–700 μm of the optic tectum (stratum fibrosum et griseum superficial and the superficial sublayer of stratum griseum centrale). The infrared cell group is found in layer 7 (a and b; stratum griseum centrale) throughout the optic tectum. Eighty percent of the infrared neurons are found within 500–1,200 μm of the surface. In layer 7b the visual and infrared cell groups are mixed; bimodal neurons that respond to a combination of visual and infrared input are located predominantly in this sublamina. The lamination pattern for visual and nonvisual cell groups in the rattlesnake tectum appears to more closely resemble the colubrid tectum and mammalian superior colliculus than the tecta of other reptiles.
The development of the hippocampus and dentate gyrus in normal and reeler mice
Authors: Stanfield Brent B. , Cowan W. Maxwell
Published: December 2004

The histogenesis, the time of origin and the pattern of migration of the cells in the hippocampus and dentate gyrus, have been studies in normal and reeler mice.

The earliest indication of a defect in the reeler hippocampus is seen on the fifteenth embryonic day (E15) which is at least 24 hours after the first indication of a defect in the neocortex. It is not until E18, that the dentate gyrus shows signs of its incipient abnormality. It appears then, in both the hippocampus and the dentate gyrus the gene defect first manifests itself at the stage at which the definitive cellular are assembled. Experiments involving the injection of 3(H‐TdR) at different developmental stages have confirmed that the site and rate of cellular proliferation in the reeler hippocampus and dentate gyrus are normal, as is the initial pattern of cell migration. However, in the reeler dentate gyrus, most postnatal cell proliferation occurs ectopically and in the hippocampus the normal “inside‐out” sequence of neurogenesis is reversed, the earliest pyramidal cells generated coming to lie superficially within the stratum pyramidale and the later formed cells being added at progressively deeper levels. There is no discernible gradient in the time of origin of the granule cells in the radial dimension of the reeler dentate gyrus, whereas there is an obvious “outside‐in” gradient in the normal animal. The characteristic gradients in cell proliferation seen in the transverse and longitudinal dimensions of the normal dentate gyrus are, however, also evident in the reeler mouse. Taken together, these observations suggest that the reeler gene exerts its effect on neuronal position only in the radial dimension, and does so at a stage of development subsequent to the proliferation and initial migration of the relevant neurons.

Timm's sulfide silver preparations indicate that the characteristic staining patterns seen in the dentate gyrus and hippocampus appear at the same time, and mature at the same rate in normal and reeler mice.
Opening of tight junctions in cerebral endothelium. II. Effect of pressure‐pulse induced acute arterial hypertension
Authors: Nagy Zoltan , Mathieson Gordon , Hüttner Istvan
Published: December 2004

Acute arterial hypertension was produced in male Wister rats by pressure pulse through the right internal carotid artery. The pressure pulse was induced by infusion of physiological saline as a bolus, at a rate of 0.63 ml per second by syringe pump. Evans blue (Eb) was used to visualize the areas of blood‐brain barrier opening. Intravenously injected horseradish peroxidase (HRP) was used to study the ultrastructural basis of permeability changes in cerebral endothelium. Eb outlined circumscribed areas of blood‐brain barrier opening. HRP extravasation was found mainly around small arteries. The capillary network was effected to a much lesser extent. Electron microscopy showed that HRP crossed the endothelial cell layer by intercellular routes. Glutaraldehyde fixed brain samples permeated with colloidal lanthanum supported these observations.