Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Callosities”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 289 records · Page 16Linked to original sources
PubMed1999

Organization of callosal connections in rats with experimentally induced microgyria.

The anatomical organization of projections from the microgyric cortex to the contralateral hemisphere through the corpus callosum has been studied in the rat. Microgyria was induced on the first postnatal day by a freezing injury. Once adult, animals received injections of horseradish peroxidase in the cortex contralateral to the lesion. Callosally projecting neurons located in the normally layered cortex adjoining the focal lesion showed a different laminar distribution from that observed in control animals. The highest percentage of callosal neurons was found in layer 6 in lesioned animals, whereas layers 2/3 and 5 gave rise to most of interhemispheric projections in controls. Possible mechanisms leading to the establishment of aberrant callosal connections and potential implications for the human pathology are discussed.

Animals↗
PubMed2004

Time-frequency analysis of visual evoked potentials for interhemispheric transfer time and proportion in callosal fibers of different diameters.

This study is an extension of the experimental research of Nalçaci et al., who presented 16 subjects with a reversal of checkerboard pattern as stimuli in the right visual field or left visual field and recorded EEG at O1, O2, P3, and P4. They applied the chosen bandpass filters (4-8, 8-15, 15-20, 20-32 Hz) to the VEPs of subjects and obtained four different components for each VEP. The first aim of this study is to improve the previous report using some methods in time-frequency domain to estimate interhemispheric delays and amplitudes in a time window. Using the improved estimates of interhemispheric delays, the second aim is to estimate the proportion of callosal fibers of different diameters that are activated by visual stimuli by comparing amplitudes of VEPs in different frequency bands. If the relation between frequency components of VEP and delays for callosal fibers of different dimension were reliable, it would give us an opportunity to deal with amplitude of bandpass-filtered VEPs in order to see approximately the proportion of these fibers activated by a certain stimulus. By using frequency-dependent shifts in time and maximizing the cross correlation of direct VEP (DVEP-VEP obtained from contralateral hemisphere)-indirect VEP (IVEP-VEP obtained from ipsilateral hemisphere) pairs in the time-frequency domain, we examined the delay not only at P100 and N160 peaks but along a meaningful time interval as well. Furthermore, by shifting back the IVEP according to the delay estimated at each time window, both the amplitudes and energies of the synchronized DVEP-IVEP pairs were compared at the chosen frequency bands. The percentages of IVEPs at each band was then examined further in conjunction with the distribution of axon diameters in the posterior pole of the CC, questioning the relation between the distributions of the axon diameters and activations at each band. We established an energy definition to express the activation in the fibers. When the energy percentages of IVEPs in theta and alpha were totaled, they were found to be between 76.2% and 81.6%, which is close to the value 74-77% for fibers of 0.4-1 microm in diameter obtained from anatomical study of human CC. The sum of energy percentages in the beta1 and beta2 bands was between 20.1% and 24.2%, which probably reflects the proportion of activation of callosal fibers 1-3 microm in diameter.

Adult↗
PubMed1997

Purification of an elicitor-induced glucan synthase (callose synthase) from suspension cultures of French bean (Phaseolus vulgaris L.): purification and immunolocation of a probable M(r)-65,000 subunit of the enzyme.

Membrane preparations from suspension-cultured cells of French bean (Phaseolus vulgaris L.) contained callose synthase (EC 2.4.1.34) activity which was preserved upon solubilisation. Following elicitor treatment of cell cultures, increased activity could be extracted and this increase was maintained during purification. The enzyme was purified by high-pressure liquid chromatography and active fractions showed a variable association of two polypeptides of relative molecular masses (M(r)) 55,000 and 65,000, the latter being in excess. The M(r)-65,000 polypeptide was purified to homogeneity and an antibody raised to it. This antibody showed complex effects on callose synthase activity when incubated with membrane and soluble extracts. In comparison with other systems, the M(r)-55,000 subunit is likely to represent the catalytic subunit while the M(r)-65,000 polypeptide is a possible regulatory subunit. The M(r)-65,000 polypeptide was immunolocated in membranes at sites of callose synthesis in the plant, in cell plates, in sieve plates, at the plasma membrane-wall interface of wounded cells and in papillae in infected cells.

Cells, Cultured↗
PubMed1998

Membrane fractionation and enrichment of callose synthase from pollen tubes of Nicotiana alata Link et Otto.

The callose synthase (UDP-glucose: 1,3-beta-D-glucan 3-beta-D-glucosyl transferase; EC 2.4.1.34) enzyme (CalS) from pollen tubes of Nicotiana alata Link et Otto is responsible for developmentally regulated deposition of the cell wall polysaccharide callose. Membrane preparations from N. alata pollen tubes grown in liquid culture were fractionated by density-gradient centrifugation. The CalS activity sedimented to the denser regions of the gradient, approximately 1.18 g.ml-1, away from markers for Golgi, endoplasmic reticulum and mitochondria, and into fractions enriched in ATPase activity and in membranes staining with phosphotungstic acid at low pH. This suggests that pollen-tube CalS is localised in the plasma membrane. Callose synthase activity from membranes enriched by downward centrifugation was solubilised with digitonin, which gave a 3- to 4-fold increase in enzyme activity, and the solubilised activity was then enriched a further 10-fold by product entrapment. The complete procedure gave final CalS specific activities up to 1000-fold higher than those of pollen-tube homogenates. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that several polypeptides co-fractionated with CalS activity through purification, with a polypeptide of 190 kDa being enriched in product-entrapment pellets.

Cell Fractionation↗
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↗
PubMed1979

The bilaminar and banded distribution of the callosal terminals in the posterior neocortex of the rat.

After callosal sectioning, the callosal connections of the posterior neocortex of the rat cerebral hemisphere were demonstrated using the Fink-Heimer technique. Serial frozen sections of the whole brains were cut in transverse, horizontal, and tangential planes. In tissue sections, degenerating terminals were concentrated in two distinct laminae within the depth of the cortex. In addition the terminals had a patchy distribution. The degeneration was marked on projection drawings of serially arranged sections, and subsequent reconstruction showed the terminal degeneration to be distributed in bands. Five dorsoventrally oriented bands of terminals were present in areas 39, 41 and 36 collectively, and a rostrocaudal band in area 20. In area 17 terminations were apparently absent except at its borders with areas 18, 18a and 7. The degenerating callosal terminals within these areas produced a circumferential band around area 17. The findings are discussed with respect to the significance of these patterns of corticocortical connections.

Afferent Pathways↗
PubMed1984

Variability in the distribution of callosal projection neurons in the adult rat parietal cortex.

Previous reports have shown that the barrel field area of the parietal cortex of the adult rat contains relatively few callosal projection neurons, even though callosal projection neurons are abundant in this cortical region in the neonatal rat. Furthermore, it has been shown that many of the callosal neurons which seem to disappear as the animal matures do not die, but project to ipsilateral cortical areas. These findings rely on the ability of retrograde transport techniques which utilize injections of horseradish peroxidase (HRP) or of fluorescent dyes into one hemisphere. We now show that several technical modifications of the HRP technique yield a wider distribution of HRP-containing neurons in the contralateral barrel field area of the adult rat than previously reported. These include implants of HRP pellets into transected axons of the corpus callosum, the addition of DMSO and nonidet P40 to Sigma VI HRP, wheat germ agglutinin HRP and the use of tetramethyl benzidine as the chromogen in the reaction procedure. Our findings have implications for transport studies in general and for the development of the cortical barrel field in particular.

Animals↗
PubMed1995

Functional significance of individual variations in callosal area.

We considered the hypothesis that the richness of callosal interhemispheric connections has a role in determining the degree of behavioural laterality and time-sharing ability in dual-task performance. Behavioural laterality as measured by dichotic word listening, line bisection and turning bias tests correlated inversely with the midsagittal cross-sectional area of the corpus callosum, as seen on MRI. The amount of dual task interference was strongly inversely correlated with the callosal area in both within-hemisphere and between-hemispheres conditions. These relationships between normal variations in callosal area, and outcomes on tests both of laterally and time-sharing capacity in normal adults suggest that the corpus callosum assumes a cross-excitatory role when subjects perform these tasks.

Adult↗
PubMed1984

The postnatal growth of the callosal connections of primary and secondary visual cortex in the rat.

The growth of callosal projections is completed earlier in primary than in secondary visual cortex. In area 17, the areal and laminar distributions of callosal projections are mature by days 9 and 12, respectively, whereas in area 18b, these developmental milestones occur by days 12 and 15, respectively. This suggests that the pruning and infiltration of callosal axons follow different schedules in different cortical areas.

Animals↗
PubMed1988

Callosal and association neurons in the cortical space: a spectral analysis approach.

The tangential distributions of callosal neurons of area 5 projecting homotopically to the contralateral hemisphere and of association neurons of areas 4 and 6 projecting to ipsilateral area 5 were determined in the macaque monkey by using neuroanatomical methods based on the retrograde transport of horseradish peroxidase. Both distributions were studied qualitatively through 2-dimensional reconstructions of the cortical areas of origin and quantitatively through a spectral analysis. This approach facilitated the characterization of the spatial periodicities contained in these distributions revealing that, in area 5, callosal neurons were organized in bands of various shapes and width; these bands were composed of more discrete clusters of cells. In the frontal lobe, association neurons projecting to ipsilateral area 5 were arranged similarly. This study suggests that a common principle underlies the tangential organization of both callosal and association projecting cells in different cortical areas and emphasizes a basic similarity of interhemispheric and intrahemispheric connections.

Animals↗
PubMed1981

The arborization of single callosal axons in the mouse cerebral cortex.

After several large cortical injections of horseradish peroxidase, individual callosal axons could be observed in most cortical areas contralateral to the injected hemisphere. They left the white matter and travelled for various distances (up to 2 mm) deep in layer VI, then turned to penetrate the cortex radially or obliquely, giving collaterals to several layers and forming narrow terminal arborisations in supragranular layers. In addition, callosal fibers were seen predominantly in deep cortical layers, which fibers could be interpreted either as collaterals of the thick fibers or as a distinct class of callosal afferents.

Afferent Pathways↗
PubMed1984

Correlation between the visual callosal connections and the retinotopic organization in striate-peristriate border region in the hamster: an anatomical and physiological study.

The correlation between the retinotopic organization of receptive fields in the striate-peristriate border region and the distribution pattern of the visual callosal projections was investigated in hamsters with corpus callosum transected 2 days before recording. The results showed that in all the animals studied, the V1/V2 border defined by reversal of receptive fields at the vertical meridian was located in the dense central portion of the visual callosal projection which terminated in cortical regions bordering areas 17 and 18a. These results indicate that there is a close relationship between the striate-peristriate border determined by anatomical and physiological methods. In addition, these data strengthen the suggestion that the pattern of visual callosal projections is a useful and reliable reference system for delineating boundaries of different visual areas in the golden hamster.

Animals↗
PubMed2006

Transhemispheric depolarizations persist in the intracerebral hemorrhage swine brain following corpus callosal transection.

Spontaneous episodes of spreading depression (SD) originating in multiple sources adjacent to a focal intracerebral hemorrhage (ICH) propagate into brain regions away from the lesion site soon after injury onset. Although these transient depolarizations have not been established in the opposite hemisphere of the swine ICH model, we have reported a diminishing of sensory responsiveness in this homotopic brain region following induction of a unilateral hemorrhage lesion. This study examined whether transient depolarizations exist in this distant brain region contralateral to the ICH site. Electrocorticographic (ECoG) recordings of brain activity were collected bilaterally from the primary somatosensory (SI) cortices of the swine brain prior to and immediately after an intracerebral injection of collagenase or saline or the insertion of the infusion pipette into the SI cortex of the right hemisphere. Transient depolarizations were present in both hemispheres of all the experimental groups. The earliest negative DC potential shifts were observed in the injured SI cortex within the first hour after collagenase injection, as compared to T = 3 h in the saline-injected group and T = 4 h in the infusion pipette only group. In contrast, transient depolarizations were first detected in the left SI cortex contralateral to the lesioned hemisphere within 2 h after collagenase infusion, by T = 4 h after saline infusion and by T = 3 h in the pipette only group. Propagating waves of negative DC potential shifts continued in both brain hemispheres, particularly in the ICH group, throughout the 11-h recording period. This novel finding of recurrent depolarizing waves in the hemisphere contralateral to the injury site prompted us to examine whether corpus callosal connections may play a role in this transhemispheric phenomenon. In a separate group of animals, the corpus callosum was transected prior to acquiring DC potential recordings and collagenase injection. The onset pattern of negative DC shifts in the callosotomized + collagenase-injected group was similar to the collagenase group with an intact corpus callosum. Initial generation of SD in the callosotomized + collagenase-injected group occurred by T = 1 h in the ICH injured right hemisphere and T = 2 h in the contralateral hemisphere. These transient depolarizations also persisted throughout 11-h recording period indicating that the corpus callosal transection did not hinder these remote propagating waves of depolarization. The presence of SD in the SI cortices of both hemispheres in all experimental groups of this study suggests that a focal mechanical or hemorrhagic injury increases the susceptibility of distant ipsilateral and contralateral brain regions to depolarizing perturbations. The mechanism for these transient depolarizations in the contralateral hemisphere apparently does not involve transhemispheric propagation along corpus callosal fibers.

Animals↗
PubMed2003

Neonatal depletion of serotonin increases the numbers of callosally projecting neurons in cat visual areas 17 and 18.

We investigated the influence of neonatal depletion of serotonin on the developmental reduction of callosal connections in cat visual cortex. Neonatal kittens were injected with 5,7-dihydroxytryptamine. At the age of 3 months, Fast Blue was injected into visual areas of one hemisphere in these and control cats and retrogradely labeled perikarya were mapped in the opposite hemisphere. In both groups callosally projecting neurons were found in a 3-5 mm wide belt centered on the transient zone of areas 17 and 18. However, numbers of labeled neurons were twice higher in the serotonin-depleted cats. We postulate that normally serotonin intensifies the process of axon pruning by augmenting developmental plasticity, therefore its depletion reduced the plasticity and more axons targeting callosal zones were stabilized, even though ectopic projections were still eliminated.

5,7-Dihydroxytryptamine↗
PubMed2006

Interhemispheric transcorpus callosal approach in the treatment of ventricular hemorrhage with obstructive hydrocephalus.

BACKGROUND: Intraventricular hemorrhage, a frequent complication of intracerebral supratentorial hemorrhage, is associated with high rates of morbidity and mortality. Several methods have recently been developed for accelerating the clearance of intraventricular blood clots, especially during massive IVH. The present study was conducted to evaluate the interhemispheric, transcorpus callosal approach with septostomy for the management of supratentorial hemorrhage with intraventricular extension. METHODS: Eighteen patients with primary IVH or thalamic/caudate hemorrhage complicated by IVH received an operation for removal of intraventricular blood clots by the interhemispheric, transcorpus callosal approach with septostomy. All patients received a brain CT examination before and after surgery. Clinical outcomes were assessed 6 months after surgery by the GOS. RESULTS: Good clinical outcomes (GOS scores >or=4) were achieved in 45.6% of patients. In the patients with poor clinical outcome, the mean age was older (P=.001) and diabetes mellitus was more common (P=.04). Patients with thalamic hemorrhage with rupture into the third ventricle had worse clinical outcomes (P=.04). The overall mortality rate at 6 months postsurgery was 5.6%. CONCLUSION: The interhemispheric, transcorpus callosal approach with septostomy is safe and effective for direct removal of intraventricular blood clots during treatment of supratentorial hemorrhage with intraventricular extension. Further investigations involving more cases are needed to assess more fully the extent of improvement in clinical outcome attributable to this approach.

Adult↗
PubMed2001

Callosal connections of the cortical taste area in rats.

The granular and dysgranular insular subregions of the cortical taste area in rats are shown to connect anatomically with the homotopical regions in the opposite hemisphere through the corpus callosum. Cells of callosal efferents and terminals of callosal fibers were found in almost all cortical layers. The findings clarify the current understanding of the morphological substrate of callosal interactions in the gustatory system.

Animals↗
PubMed2001

Callosal transfer in different subtypes of developmental dyslexia.

Sixteen controls (age 6-13) and 20 native Italian children with developmental dyslexia (age 7-15) received a test of callosal transfer of tactile information. Among the dyslexic children, 7 had a diagnosis of L-type, 7 of P-type and 6 of M-type dyslexia according to Bakker's classification. Both control children and children with dyslexia made a significantly larger number of errors in the crossed localization condition (implying callosal transfer of tactile information) vs. the uncrossed condition. In the same condition, children with dyslexia made a significantly larger number of errors than controls. In the crossed localization condition L-types and M-types made a significantly larger number of errors than P-types and controls, while there was no significant difference in performance between P-types and controls. These findings are discussed in terms of defective callosal transfer or deficient somatosensory representation in children with L- and M-dyslexia.

Adolescent↗
PubMed1989

The effects of total and partial callosal agenesis on the development of morphological brain asymmetries in the BALB/cCF mouse.

The corpus callosum fails to develop in some mice of the BALB/cCF strain. We report here a study on cerebral morphological asymmetry in males of this particular strain in order to test the hypothesis that the normal development of the corpus callosum is responsible for the establishment of brain asymmetries. In 46 animals the dorsal area and the weight of each hemisphere were measured. In order to identify the animals with callosal defects and check for size anomalies of the anterior commissure, the hemispheres were cut into sagittal sections and stained with cresyl violet. Measures of sagittal area of the anterior commissure did not support the hypothesis that this commissure is enlarged when the corpus callosum is reduced or absent. In normal animals, the mean difference between left and right dorsal cortical areas showed a significant directional asymmetry, the left being consistently greater than the right. A similar pattern was found for weight. In mice with callosal defects there were no significant differences, either between the dorsal areas or between the weights of the hemispheres. However, data on the absolute values of the hemispheric differences indicated the presence of a nondirectional asymmetry not only in normal animals, but also in mice with callosal defects. Therefore, our data suggest that the ontogenesis of the corpus callosum plays a role in directing the development of cerebral asymmetries.

Agenesis of Corpus Callosum↗