SEARCH · PubMed Health

Results for “Callosities”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources

PubMed1992

Development of callosal connections in the sensorimotor cortex of the hamster.

To investigate the development of corpus callosal connectivity in the hamster sensorimotor cortex, we have used the sensitive axonal tracer 1,1 dioctadecyl-3,3,3',3', tetramethylindocarbocyanine perchlorate (DiI), which was injected either in vivo or in fixed brains of animals 3-6 days postnatal. First, to study changes in the overall distribution of developing callosal afferents we made large injections of DiI into the corpus callosal tract. We found that the anterogradely labeled callosal axons formed a patchy distribution in the contralateral sensorimotor cortex, which was similar to the pattern of adult connectivity described in earlier studies of the rodent corpus callosum. This result stands in contrast to previous retrograde studies of developing callosal connectivity which showed that the distribution of callosal neurons early in development is homogeneous and that the mature, patchy distribution arises later, primarily as a result of the retraction of exuberant axons. The initial patchy distribution of callosal axon growth into the sensorimotor cortex described in the present study suggests that exuberant axons destined to be eliminated do not enter the cortex. In addition, small injections of DiI into developing cortex resulted in homotopic patterns of callosal topography in which reciprocal regions of sensorimotor cortex are connected, as has been shown in the adult. Second, to study the radial growth of callosal afferents we followed the extension of individual callosal axons into the developing cortex. We found that callosal axons began to invade the contralateral cortex on about postnatal day 3, with little or no waiting period in the callosal tract. Callosal afferents then advanced steadily through the cortex, never actually invading the cortical plate but extending into layers on the first day that they could be distinguished from the cortical plate. The majority of callosal axons grew radially through the cortex and did not exhibit substantial branching until postnatal day 8, the age when the cortical plate disappears and callosal afferents reach the outer layer of cortex. This mode of radial growth through cortex prior to axon branching could serve to align callosal afferents with their radial or columnar targets before arborizing laterally.

Anesthesia↗

PubMed1979

The anatomical substrate of callosal messages from SI and SII in the cat.

Horseradish peroxidase (HRP) was injected into the first (SI) or second (SII) somatosensory areas of 21 adult cats. The radial and tangential (normal and parallel to the pial surface, respectively) distribution and morphology of the callosal neurons were studied. HRP injections were combined with single unit recording in the contralateral cortex in order to determine which part of the somatosensory periphery is represented within the regions containing callosal neurons, the callosal (efferent) zones, in SI and SII. The callosal zone of SI extends over the trunk and part of the forepaw representation. In the forepaw and hindlimb representations callosal neurons projecting only to the contralateral SII are found, while in the trunk representation callosal neurons projecting to contralateral SI or SII are found. The callosal zone in SII extends widely throughout the forepaw representation in this area and projects to the contralateral SII but not to SI. In both SI and SII the callosal neurons are mainly located in layer III. A few of them are also found in layer VI. They are very rare in other layers. Callosal neurons in layer III are mostly pyramidal but exceptionally stellate; in layer VI they are pyramidal, triangular, and occasionally stellate. These data indicate that transformations of the cortical somatosensory maps are achieved in the message sent through the corpus callosum. These transformations are i) determined by the extent and location of the callosal zones and perhaps by the distribution of callosal neurons within them, ii) different in different areas, iii) different in a same area, according to the cortical targets to which they are conveyed. The existence of callosal connections originated from areas of distal forepaw representation supplies a possible anatomical substrate for those types of intermanual transfer of tactile learning which depend upon the integrity of the corpus callosum.

Animals↗

PubMed1978

Sources and terminations of callosal axons related to binaural and frequency maps in primary auditory cortex of the cat.

The distributions of sources and terminals of callosal fibers in the high-frequency representation of AI were related to binaural and frequency maps in combined anatomical and electrophysiological experiments. Sources of callosal axons were retrogradely labeled with HRP. Distributions of axon terminals were determined by autoradiographic labeling with [3H]-proline and anterograde degeneration following callosal section. Regions in which cells exhibit summation or ipsilateral dominance and suppression contain higher concentrations of sources and terminals of callosal fibers than do regions in which cells exhibit monaural contralateral responses or contralateral dominance and suppression. Callosal axon terminals aggregate into columns. In sections cut parallel to the cortical surface callosal columns take on complex forms that exhibit certain consistent features. Two prominent elongated columns separated by a narrow zone of sparse callosal innervation run in a rostrodorsal to caudoventral direction through AI crossing several octaves of the frequency representation. Ventral to these columns, along the AI-AII border, less densely labeled callosal columns are in evidence. Low frequency representations of AI are interconnected but details of their innervation patterns were not worked out. Outside of AI there are regions that contain complex configurations of callosal columns. Several morphologically distinct types of neurons, located in laminae III through VI, were retrogradely labeled following injections of HRP into the opposite AI. About 94% of callosal neurons are pyramidal cells of layers III and IV.

Animals↗

PubMed1992

Topographic organization, number, and laminar distribution of callosal cells connecting visual cortical areas 17 and 18 of normally pigmented and Siamese cats.

The callosal connections between visual cortical areas 17 and 18 in adult normally pigmented and "Boston" Siamese cats were studied using degeneration methods, and by transport of WGA-HRP combined with electrophysiological mapping. In normal cats, over 90% of callosal neurons were located in the supragranular layers. The supragranular callosal cell zone spanned the area 17/18 border and extended, on average, some 2-3 mm into both areas to occupy a territory which was roughly co-extensive with the distribution of callosal terminations in these areas. The region of the visual field adjoining the vertical meridian that was represented by neurons in the supragranular callosal cell zone was shown to increase systematically with decreasing visual elevation. Thus, close to the area centralis, receptive-field centers recorded from within this zone extended only up to 5 deg into the contralateral hemifield but at elevations of -10 deg and -40 deg they extended as far as 8 deg and 14 deg, respectively, into this hemifield. This suggests an element of visual non-correspondence in the callosal pathway between these cortical areas, which may be an essential substrate for "coarse" stereopsis at the visual midline. In the Siamese cats, the callosal cell and termination zones in areas 17 and 18 were expanded in width compared to the normal animals, but the major components were less robust. The area 17/18 border was often devoid of callosal axons and, in particular, the number of supragranular layer neurons participating in the pathway were drastically reduced, to only about 25% of those found in the normally pigmented adults. The callosal zones contained representations of the contralateral and ipsilateral hemifields that were roughly mirror-symmetric about the vertical meridian, and both hemifield representations increased with decreasing visual elevation. The extent and severity of the anomalies observed were similar across individual cats, regardless of whether a strabismus was also present. The callosal pathway between these visual cortical areas in the Siamese cat has been considered "silent," since nearly all neurons within its territory are activated only by the contralateral eye. The paucity of supragranular pyramidal neurons involved in the pathway may explain this silence.

Albinism↗

PubMed1976

Callosal transfer of impulses originating from superficial and deep nerves of the cat forelimb.

1. Experiments were performed in 18 chloralose-anaesthetized, curarized cats in order to study the callosal transfer of somatic information originated in exteroceptive and proprioceptive receptors. Several cutaneous and deep nerves of the forelimb were prepared and stimulated with graded intensities, so as to activate selectively afferent fibres pertaining to the different groups of Lloyd's classification. Simultaneous records were taken (and averaged on-line by means of a multichannel analyzer) from the distal end of a cut dorsal rootlet (C7-C8), from the cerebral cortex (SI, SII or area 3a, according to the experiment) and from the somesthetic callosal region (SCR). 2. The low-threshold afferent fibres (Group II) of cutaneous origin were found to have a wide projection to the SCR, with the maximal density in its middle portion. Some of the fastest corticocallosal impulses are relayed monosynaptically at cortical level. Plots of the amplitude of cortical and callosal responses as a function of stimulus strength showed that both central responses have the same threshold and exhibit a parallel, sharply-rising amplitude increase, thus suggesting that the cortico-callosal re-transmission system for afferent impulses of cutaneous origin is very powerful in nature. Impulses elicited in afferent fibres of higher threshold (Group III) do not enhance the cortical and callosal positive waves provoked by Group II afferent volleys. 3. Afferent fibres of deep origin were also found to send a wide projection to the SCR, although less substantial than that of cutaneous fibres. Stimulation of the deep radial nerve elicited mass responses in the whole SCR, provided the strength of stimuli was high enough to engage the Group II fibres. Only in the central portion of the SCR were small potentials recorded in response to pure Group I volleys of DRN. Experiments performed with selective stimulation of pure muscular branches of forelimb deep nerves as well as of articular and mixed (muscular and articular) branches gave evidence making it possible to ascertain the origin of deep afferent fibres projecting to the SCR. Stimulation of the forelimb muscular branches with strength provoking full activation of Group I afferent and additional engagement of those of Group II, did not provoke mass responses in the whole extent of the SCR. In order to obtain callosal potentials upon stimulation of pure muscular nerves, it was necessary to increase the stimulus strength at or above the threshold for Group III fibres. On the contrary, the same callosal foci unresponsive to Group I and II muscular afferent volleys exhibited clear-cut responses to stimulation of the lowest-threshold Group I and/or Group II afferents of articular and mixed nerves. From the results it might be inferred that only proprioceptive information originating from articular receptors and from extrafusal muscular afferents has access to the callosal interhemispheric transfer.

Animals↗

PubMed1991

Segregation of callosal and association pathways during development in the visual cortex of the primate.

The segregation of callosal and association pathways in the developing visual cortex of the monkey was studied using the retrograde tracers fast blue and diamidino yellow. Quantitative analysis of the laminar distribution of labeled callosal and association neurons made it possible to reveal the shifting pattern of connections that characterizes the development of these two pathways. In the adult, callosal neurons are restricted to supragranular layers, where they are concentrated at the bottom of layer 3. Association neurons are located both in infra- and supragranular layers. Supragranular layer association neurons are concentrated in layer 2, with limited spread into layer 3 so that there is little overlap with callosal neurons. In the immature brain, callosal neurons are characterized by a tangential distribution that is more widespread than in the adult, while their laminar distribution undergoes little developmental change. Association neurons show two types of changes in their laminar distribution: (1) in the early fetus, there is a large excess of association neurons in supragranular layers, the adult distribution being achieved some time after birth; and (2) during maturation there is a selective elimination of at least 50% of the projections originating from the lower part of layers 2/3. Hence, the adult radial segregation of association and callosal pathways is achieved in part by regressive phenomena. The developmental reduction of bihemispheric projections is largely independent of changes in the organization of association neurons. Quantitative analysis of the morphology and spatial location of neurons sending axon collaterals to both hemispheres suggests that they constitute a subset of callosal neurons and that their frequency is determined by factors that regulate directly this population. These results are discussed with respect to the specification of visual cortical pathways during ontogenesis.

Amidines↗

PubMed1992

Emergence of callosally projecting neurons with stellate morphology in the visual cortex of the kitten.

Callosally projecting neurons in areas 17 and 18 of the adult cat can be classified into two types on the basis of their dendritic morphology: pyramidal and stellate cells. The latter are nearly exclusively of the spinous type and are predominantly located in upper layer IV. Retrograde transport of the carbocyanine dye DiI, applied to the corpus callosum, showed that, up to P6, all callosally projecting neurons resemble pyramids in the possession of an apical dendrite reaching layer I. At P10, however, callosally projecting neurons with stellate morphology were found. A study was designed to distinguish whether these neurons are late in extending their axons to the corpus callosum or, alternatively, have transient apical dendrites. To this end, callosally projecting neurons were retrogradely labeled by fluorescent beads injected in areas 17 and 18 at P1-P3 and then either relabeled with DiI applied to the corpus callosum at P10 or intracellularly injected with Lucifer Yellow at P57. Double-labeled stellate and pyramidal cells were found in similar proportions to those found for the total, single-labeled population of callosally projecting neurons. It is therefore concluded that callosally projecting spiny stellate cells initially possess an apical dendrite and a pyramidal morphology. At P6, i.e. close to the time when stellate cells appear, layer IV neurons with an atrophic apical dendrite were found, suggestive of an apical dendrite in the process of being eliminated.

Animals↗

PubMed1992

Long-term callosal lesions and learning of a black-white discrimination by one-eyed rats.

We know from our previous studies that mature rats with monocular enucleation at birth (OEBs), as well as animals enucleated at maturity (OETs), were unable to learn a black-white discrimination when they were trained after lesions of the visual cortex contralateral to the remaining eye. Since it is well known that synaptic reorganization takes place in the adult rat brain through reactive synaptogenesis following deafferentation, we wondered if long-term callosal lesions in OEBs and OETs would bring out such synaptic reorganization in the visual cortex and, consequently, affect the outcome of the discrimination mentioned above. In the present study, two experiments were carried out: in Experiment 1 the previous experiment was replicated in that OEBs and OETs of 3 months of age were trained on the discrimination 10 days following unilateral visual cortex lesions; in Experiment 2, effects of callosal lesions made 10 weeks earlier either at 3 weeks of age or 13 weeks of age were investigated. The results were: 1) the findings of the previous experiment were confirmed; 2) the long-term callosal lesions facilitated the acquisition of discrimination in OEBs but not in OETs; 3) the facilitative effects were more prominent in OEBs with callosal lesions at 3 weeks of age than in those at 13 weeks of age. The findings were discussed in relation to possible synaptic reorganization produced in the visual cortex ipsilateral to the remaining eye following callosal lesions made 10 weeks earlier and also in relation to reorganization of the uncrossed visual pathways resulting from monocular enucleation at birth.

Aging↗

PubMed2026

A conserved COBL3-like protein promotes PDLP5-dependent callose accumulation to confer broad-spectrum plasmodesmata-mediated antiviral defense.

Plasmodesmata (PDs) play vital roles in plant growth and defense by controlling the symplastic transport of important molecules. Here we report that a conserved COBRA-like protein, COBL3, positively regulates callose accumulation and is required for PD-mediated antiviral defense (PMAD) against divergent plant RNA viruses in wheat (Triticum aestivum) and tobacco (Nicotiana benthamiana). The wheat COBL3 protein, TaCOBL3, interacts with the 17K movement protein (MP) of barley yellow dwarf virus-GAV (BYDV-GAV). TaCOBL3 is associated with the plasma membrane and co-localizes with 17K MP at PDs. Genetic analysis with overexpression and knockout lines revealed that TaCOBL3 positively regulates wheat defense against BYDV-GAV by modulating callose accumulation at PDs. Interestingly, TaCOBL3 interacts with the wheat homolog of PDLP5, a conserved key regulator of PD permeability in higher plants. Silencing TaPDLP5 attenuates the elevated BYDV-GAV defense conferred by overexpression of TaCOBL3 in wheat. Furthermore, transient expression of TaCOBL3 promotes callose accumulation and lowers PD permeability in tobacco cells, and these effects are largely compromised when tobacco PDLP5 is silenced. Notably, BYDV 17K MP weakens the interaction between TaCOBL3 and TaPDLP5 and inhibits their callose-binding activities. Finally, silencing of tobacco NbCOBL3 reduces callose content and attenuates host defense against two tobraviruses, one potexvirus, and one hordeivirus. Overall, our study reveals a previously unknown role of COBRA-like proteins in PMAD and provides insight into how a plant viral MP sabotages PMAD by perturbing the COBL3-PDLP5 interaction to facilitate virus spread through PDs. The conserved COBL3 gene may be a valuable target for engineering of broad-spectrum antiviral resistance in crop plants.

COBRA-like protein↗

PubMed1992

Premature dissolution of the microsporocyte callose wall causes male sterility in transgenic tobacco.

Male sterility in a petunia cytoplasmic male sterile line has been attributed to the early appearance of active callase, a beta-1,3-glucanase, in the anther locule. This leads to premature dissolution of the callose walls surrounding the microsporogenous cells. We have mimicked this aspect of the petunia line in transgenic tobacco by engineering the secretion of a modified pathogenesis-related vacuolar beta-1,3-glucanase from the tapetum prior to the appearance of callase activity in the locule. Plants expressing the modified glucanase from tapetum-specific promoters exhibited reduced male fertility, ranging from complete to partial male sterility. Callose appearance and distribution are normal in the male sterile transgenic plants up to prophase I, whereupon callose is prematurely degraded. Meiosis and cell division occur normally. The resultant microspores have an abnormally thin cell wall that lacks sculpturing. The tapetum shows hypertrophy. Male sterility is probably caused by bursting of the aberrant microspores at a time corresponding to microspore release. These results demonstrate that premature callose degradation is sufficient to cause male sterility and suggest that callose is essential for the formation of a normal microspore cell wall.

Base Sequence↗

PubMedDate not supplied

Apparent atypical callosal dysgenesis: analysis of MR findings in six cases and their relationship to holoprosencephaly.

The MR scans of six pediatric patients with apparent atypical callosal dysgenesis (presence of the dorsal corpus callosum in the absence of a rostral corpus callosum) were critically analyzed and correlated with developmental information in order to assess the anatomic, embryologic, and developmental implications of this unusual anomaly. Four patients had semilobar holoprosencephaly; the dorsal interhemispheric commissure in these four infants resembled a true callosal splenium. All patients in this group had severe developmental delay. The other two patients had complete callosal agenesis with an enlarged hippocampal commissure mimicking a callosal splenium; both were developmentally and neurologically normal. The embryologic implications of the presence of these atypical interhemispheric connections are discussed. Differentiation between semilobar holoprosencephaly and agenesis of the corpus callosum with enlarged hippocampal commissure--two types of apparent atypical callosal dysgenesis--can be made by obtaining coronal, short TR/TE MR images through the frontal lobes. Such differentiation has critical prognostic implications.

Abnormalities, Multiple↗

PubMed2026

A CsWRKY46-CsPBL9-CsARI1 tripartite regulatory module coordinates H2O2 production and callose deposition in citrus fruit immunity.

Plant immunity against pathogens involves multiple immune responses and intricate regulatory networks. However, how immune networks are deployed in fruit remains poorly understood. Here, we show that citrus fruit immune responses, including hydrogen peroxide (H2O2) production and callose deposition, are multiply regulated by transcriptional activation, phosphorylation, and ubiquitination. Citrus sinensis genes encoding nicotinamide adenine dinucleotide phosphate (NADPH) oxidase CsRBOHG and callose synthase CsCalS5, responsible for H2O2 production and callose deposition, respectively, are transcriptionally activated by CsWRKY46. Phosphorylation-enhanced activity of CsRBOHG by CsPBL9 enhances immunity. RING1-IBR-RING2 (RBR)-type E3 ligase CsARI1, acting as an immune brake, ubiquitinates CsRBOHG and CsCalS5 for degradation. Interestingly, CsARI1 also shows a moonlight function wherein it interacts with CsPBL9 in a non-ubiquitination manner, disrupting CsPBL9's interaction with CsRBOHG. This CsARI1-CsPBL9 interaction is stimulated by H2O2 as feedback. Moreover, H2O2 contributes to callose deposition, indicating an interplay between two immune responses. Our study reveals a tripartite regulatory hub orchestrating self-linked immunity in citrus fruit.

CP: plants↗

PubMed2025

Translation Co-factor PABP-interacting protein 11 moonlights as a transcriptional activator to modulate callose synthesis gene expression.

The development of rice fertility is a complex process, which is precisely regulated by numerous genes. In this study, we cloned and characterized OsPAIP11, a PABP-interacting protein that functions as an auxiliary factor in translation initiation. The ospaip11 exhibited multiple defects, including impaired callose synthesis, delayed tapetum apoptosis, and abnormal pollen wall development, which are essentially consistent with the phenotype of the allelic mutant dcet1. Subcellular localization analysis revealed that OsPAIP11 is localized in both the cytoplasm and nucleus. Interestingly, further investigation demonstrated that the RRM2 domain of OsPAIP11 exhibits transcriptional activation activity. Moreover, OsPAIP11 directly binds to the promoter of the callose synthesis-related genes GLUCAN SYNTHASE-LIKE 5 (OsGSL5) and OsGAMYB, thereby regulating their transcription and influencing callose biosynthesis during pollen development. Additionally, OsPAIP11 also interacts with the translation initiation factor and auxiliary factors. These findings suggest that OsPAIP11 modulates male fertility primarily by regulating the transcription of callose synthesis-related genes and may also participate in the translation process.

Glucans↗

PubMed1992

Postnatal development of area 17 callosal connections in Tupaia.

The goal of the present study was to investigate the pattern of maturation of callosal projecting neurons in a well-studied mammalian visual system with unique structural and functional properties. Studies of the distribution pattern of interhemispheric connections in the adult tree shrew primary visual cortex reveal not only a high concentration of labeled neurons along the area 17/18 border, as in standard experimental animals such as the cat and monkey, but also numerous callosal projecting neurons in the adjacent dorsal part of area 17, which largely corresponds to the binocular visual field (Kretz and Rager, Exp. Brain Res. 82:271, '90). Callosal projections were anatomically traced in 11 tree shrews (Tupaia belangeri) at various ages between postnatal day 7 (7, 9, 10, 13, 15, 17, 19, and 26 days old) and adulthood (107 days old). In each animal, four injections of wheat germ agglutinin conjugated to horseradish peroxidase were made in a standard configuration into the striate cortex of one hemisphere. In young tree shrews only 7 and 9 days old, heavily labeled terminal axon structures could be seen in the white matter and in layer VI of the opposite hemisphere. Only a few labeled neurons, however, were detected in layer III. The small number of labeled neurons indicated that early in postnatal development, only a few callosal axons had invaded the upper cortical layers. By 10 days of age, the number of supragranular neurons was increasing and the maximal value was counted in a 13-day-old tree shrew. A sharp decline in the number of labeled supragranular neurons was noticed--about 94% in our case--between days 13 and 15. In animals more than 15 days old, the distribution pattern and the density of the neurons looked like the pattern seen in the adult Tupaia brain. The labeled cells were mostly concentrated in layers II and III. The majority of neurons resembled typical pyramidal cells. However, some of the neurons in sublayer IIIc had elongated cell bodies oriented parallel to the laminar boundaries. In contrast to the supragranular cells found in all stages investigated, small populations of labeled cells in layer VI were observed in 9- to 17-day-old tree shrews only. In young postnatal animals 7 to 13 days old, a peculiar cell type was labeled on the ipsilateral side. In coronal sections these cell bodies formed a continuous band that extended from the ventricular wall to the subcortical white matter. These cells might belong to a population of cells still in migration.

Animals↗

PubMed1992

Visual callosal projections in the adult ferret.

The laminar and tangential organization of visual callosal projections of areas 17 and 18 were investigated in the adult ferret, using histochemical methods to visualize axonally transported horseradish peroxidase (HRP). Normal adult ferrets were given injections of HRP throughout one visual cortex or had gelfoam soaked in HRP applied to the transected corpus callosum. The ferret callosal cell distribution has a greater tangential extent in area 18 than in area 17. In addition, the radial organization of callosal cells in areas 17 and 18 differs: three times as many infragranular cells are present in area 18 than in area 17, although the number of supragranular cells is similar for both areas 17 and 18. Since the projections of alpha retinal ganglion cells are reported to be exclusively contralateral in the ferret (Vitek et al., 1985), callosal projections may make a major contribution to the binocularity of neurons in area 18.

Animals↗

PubMed1992

[MR imaging of corpus callosal injuries].

The MR imaging and CT findings of corpus callosal injury were analyzed in 32 of 224 patients with acute head injuries. MR imaging was more sensitive than CT in the detection of callosal injuries. All 9 hemorrhagic lesions were visualized on both MR imaging and CT. Fifteen of 23 nonhemorrhagic lesions were not visualized on CT, although all nonhemorrhagic lesions were visualized on MR imaging. Twenty-four lesions of the corpus callosum were located in the splenium, but no lesion was located in the rostrum. Diffuse axonal shear injuries were visualized in 25 patients with callosal injury as associated traumatic lesions. Twenty-three patients with callosal injury had low initial Glasgow Coma Scale scores (less than 9), but 9 patients had high scores. Associated diffuse axonal shear injuries, especially in the brain stem could be a possible explanation for this difference. MR imaging is useful to detect traumatic lesions of the corpus callosum.

Accidents, Traffic↗

PubMed1992

Types of callosally projecting nonpyramidal neurons in rat visual cortex identified by lysosomal HRP retrograde labeling.

Callosally projecting neurons, labeled following injection of horseradish peroxidase (HRP) into the 17/18a border of the contralateral hemisphere, have been examined by light and electron microscopy. These neurons exhibit two types of horseradish peroxidase labeling: either a diffuse, Golgi-like labeling, or a granular, punctate labeling. The punctate type of HRP-labeling is the predominant form in nonpyramidal neurons, while pyramidal neurons frequently display either diffuse or punctate labeling. Only punctately labeled neurons have been examined in this study. Light microscopic analyses of 1-microns sections show that in the heavily labeled zone at the area 17/18a border approximately 9% of all of the cells in layer II/III are callosally projecting nonpyramidal cells, and 70% of them are callosally projecting pyramidal cells. Light and electron microscopic examinations indicate that the nonpyramidal neurons are a heterogeneous group which consists of small multipolar neurons, large multipolar neurons, small bipolar neurons, and large bipolar neurons. To investigate the ultrastructural appearance of the punctate HRP labeling, selected neurons have been examined in thin sections. In the electron microscope, the tetramethylbenzidine (TMB) reaction product appears as electron-dense crystals, while the diaminobenzidine (DAB) reaction product appears as dark, electron-dense material which fills the lysosomes. These lysosomes occasionally have a halo of reaction product, but often they are not morphologically distinguishable from dark lysosomes present within neurons from control animals in which the darkening results from staining the thin sections with lead citrate and uranyl acetate. However, labeled neurons possess more dark lysosomes than neurons from control animals. These additional dark lysosomes presumably contain the HRP reaction product visible by light microscopy.

Animals↗

PubMed1975

Intermanual transfer in the monkey as a function of amount of callosal sparing.

The effects of commissure section, task difficulty and overtraining on the intermanual transfer of tactile learning have been examined. Twenty-one rhesus monkeys were allocated to 4 groups. One group was subjected to complete transection of the corpus callosum, massa intermedia and posterior commissure. Some of this group also sustained a cerebellar section. A second group received a similar division of the commissures but with part of the posterior body of the corpus callosum left intact. A third group received similar division of the commissures but with the posterior commissure left intact. The fourth group formed an unoperated control group. Animals with only the posterior commissure left intact showed little or no transfer. Animals with partial callosal lesions showed significantly greater transfer than animals with total transections, but were impaired relative to the unoperated controls. Estimates have been made of the number of callosal fibres left intact in the animals with partial callosal lesions. These estimates have been correlated with transfer. The correlation was significant on only one task. Neither task difficulty nor overtraining were found to affect transfer significantly. The comparison of transfer of the submodalities of size and roughness was inconclusive.

Animals↗