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PubMed1989

Glutamate and aspartate immunoreactivity in cortico-cortical neurons of the sensorimotor cortex of rats.

Retrograde transport of tracers and immunocytochemistry have been used to determine if association and callosal neurons in the primary motor and somatosensory cortex of rats contain high levels of glutamate or aspartate and may, thus, use these amino acids as neurotransmitter. After tracer injections in these areas, about 65% of the retrogradely labeled neurons in layer V in the ipsilateral or contralateral hemisphere are immunopositive for glutamate. Lower percentages of double-labeled neurons are found in layers III, VI, and II. Similar results are obtained when sections are processed for aspartate immunoreactivity. About 90% of retrogradely labeled neurons are immunopositive in sections incubated with a mixture of both glutamate-and aspartate antisera. These results suggest that a large fraction of cortico-cortical neurons are immunoreactive for either one amino acid but not for both. It is proposed that neurons with high levels of one amino acid use this as neurotransmitter; high levels of glutamate and aspartate are likely to be present in a fraction of neurons which may release both amino acids or a substance closely related to these.

Amidines↗
PubMed1989

Nucleotide sequence and regulated expression of a wound-inducible potato gene (wun1).

Mechanical wounding of potato leaves, stems, roots and tubers leads to a rapid increase of wun1 mRNA. In potato leaves, the wound-induced accumulation of wun1 mRNA is inhibited by the addition of sucrose or other osmotically active agents. This inhibition is organ specific since sucrose does not prevent wun1 mRNA accumulation in wounded tubers. In contrast, expression of patatin was shown to be repressed in tubers by wounding and this repression was reversed by increasing osmotic pressure. Sequence data obtained from the analysis of a wun1 cDNA and a wun1 genomic clone show no homology to any gene known so far. Histochemical data demonstrate a striking analogy in cell specific expression of chimeric genes expressed under the control of the wun1 promoter and the cell specific production of callose in wounded tobacco leaves.

Amino Acid Sequence↗
PubMed1987

Thalamo-cortical connections and their correlation with receptive field properties in the cat's lateral suprasylvian visual cortex.

Areas PMLS and PLLS of the cat's lateral suprasylvian visual cortex display an interesting global organization of local features in their single unit response properties: direction preference is centrifugally organized and velocity preference increases with eccentricity. In addition it has previously been shown that binocular interactions are strongest around the visual field center. This characterizes the LS areas as apt for the analysis of optic flow fields and for visual processing in various kinds of visuomotor tasks (Rauschecker et al. 1987). In the present study we analysed the types of input to LS from the optic chiasm, the corpus callosum and from two thalamic relay nuclei (lateral posterior and lateral geniculate) that constitute important sources of afferent information to the LS areas. We were interested in learning how the afferent (and efferent) connections between LS and these structures relate to the response properties of LS neurons. Overlap of an RF into the ipsilateral hemifield was virtually always associated with callosal input. Latency differences between responses to electrical stimulation of the optic chiasm and the thalamic sites indicated almost exclusively fast-conducting Y-input to LS. Correlation of response latencies with receptive field properties revealed the following correspondences: A positive correlation was found between LP-latency and RF-size matching the dependence of RF size on laminar origin. The type of correlation found between LP-latency and directional tuning of LS cells suggests that an interaction between thalamic and other inputs may be responsible for direction selectivity in LS. Finally, correlation of LP-latencies with centrifugal direction preference suggests that this specific property is generated by intracortical wiring rather than by thalamic input.

Action Potentials↗
PubMed1987

The treatment of hallux valgus in runners using a modified McBride procedure.

We have carried out a modified McBride procedure in 21 patients with hallux valgus which caused pain during running. They have been followed up for a mean of 5.5 years. Metatarsophalangeal pain and metatarsalgia were relieved or significantly decreased in the majority of patients, but callosities beneath the second metatarsal head were not affected. When the angle between the first and second metatarsals did not exceed 14 degrees before operation, satisfactory correction could be obtained. In the absence of degenerative changes in the first metatarsophalangeal joint and with a moderate hallux valgus, a consistently good result was obtained in this group of active patients.

Adolescent↗
PubMed1988

Bilateral receptive fields of cells in rat Sm1 cortex.

Single cells in the primary somatosensory (Sm1) cortex were investigated for responses to bilateral hindpaw stimulation in Wistar rats anaesthetised by continuous intravenous administration of Althesin. Fifty-one percent of cells sampled (N = 134) responded to equivalent punctate mechanical stimuli delivered to both the contralateral and ipsilateral hindpaws under light anaesthesia. The distribution by cortical depth of cells with receptive fields (RFs) on both hindpaws was not significantly different from cells which had only contralateral RFs. No cell was found with a purely ipsilateral RF. For 86% of cells tested (N = 44) the ipsilateral RF was partly or completely homologous with areas within the contralateral RF. The sizes of ipsilateral RFs were smaller on 66% of occasions when tested against their contralateral RFs. Modal latencies to ipsilateral mechanical stimulation were longer than to contralateral stimulation (34.1 +/- 9.1 ms (S.D) cf. 26.4 +/- 7.2 ms, N = 44). Ipsilateral RFs were lost for 77% of cells tested following a 33% increase in anaesthetic infusion rate. Conditioning mechanical stimuli applied to the centre receptive field (CRF) on the ipsilateral hindpaw reduced or abolished a cell's responses to equivalent test stimuli applied to it's contralateral CRF with C-T intervals of 20-200 ms. Conditioning stimuli applied to the CRF contralateral to the cell reduced or abolished responses to test stimuli on the cell's ipsilateral CRF using C-T intervals of 0-900 ms. Responses in one cortex to stimulation of the ipsilateral hindpaw were unaffected by elimination of responses from the same hindpaw in the opposite contralateral Sm1 cortex, where responses had been suppressed by topical Lignocaine administration. Retrograde transport of horseradish peroxidase from hindpaw Sm1 cortex labelled many cells in homolateral thalamus, but failed to label cells in the entire forebrain contralateral to the injection site. It is concluded that direct crossed thalamo-cortical and callosal Sm1-Sm1 pathways do not contribute to the production of hindpaw ipsilateral receptive fields.

Animals↗
PubMed1985

The development of commissural connections of somatic motor-sensory areas of neocortex in the North American opossum.

The North American opossum does not have a corpus callosum; neocortical commissural axons are contained entirely within the anterior commissure. We have used axonal transport techniques to study the origin and distribution of commissural axons from somatic motor-sensory cortex in developing and adult opossums. Neocortical axons grow into the anterior commissure by postnatal day (PND) 12, the contralateral external capsule by approximately PND 19, the area deep to the contralateral homotypic cortex by approximately PND 26 and the cortex proper by approximately PND 35. Commissural neurons were first demonstrated at about PND 26, when they form a fairly continuous band in the cortical subplate (presumptive layers V-VI). By at least PND 37, commissural neurons are also present in layers II and III, where they form a continuous band, and in layer IV, where they are sparse. In older pouch young and adult opossums the bands of commissural neurons, especially in layers V-VI, are interrupted, and commissural neurons are rare in layer IV. In general, commissural axons in both pouch-young and adult opossums innervate areas containing commissural neurons as well as layer I. In the acallosal opossum as well as in the callosal rat, the development of commissural connections from somatic motor-sensory cortex is characterized by pauses during the growth of axons into the opposite cortex, by a general inside-out-gradient, and by a transition from continuous bands to patchy, radial columns of commissural neurons and axons. This suggests that similar mechanisms govern the formation of commissural connections in the two species.

Animals↗
PubMed1993

Primary brain stem lesions caused by closed head injuries.

Traumatic lesions of the brain stem are of two types: primary, which are considered to be caused at the moment of impact, and secondary, associated with supratentorial mass lesion. Of the 239 patients with a serious head injury who showed a severe disturbance of consciousness upon admission and who had CT scan carried out immediately, 21 cases were considered to have a primary brain stem lesion with initial CT scan. A primary brain stem lesion was found in 21 of 239 (8.8%) of patients with serious head injury. Their injuries were caused primarily by traffic accidents. Sixteen of the 21 cases showed not only brain stem lesions but also other brain injuries such as cerebral contusion of the white and gray matter, callosal injury, intraventricular hemorrhage, and subarachnoid hemorrhage, which are considered to be caused by a diffuse shearing injury. Five cases who showed a single injury to the brain stem with no other brain lesions were considered to have a pure brain stem lesion. Primary brain stem lesions were observed on the dorsal side of the midbrain, where they can be differentiated from secondary brain stem lesions. These lesions are considered to result from the shearing mechanism in and around the brain stem very close to the tentorial edge, or to an injury of the lower brain stem by hyperextension of the cervical vertebrae. The prognosis of patients with a primary brain stem lesion was usually unfavorable, except in those with a single brain stem lesion.

Adolescent↗
PubMed1995

MRI of pineal region tumours: relationship between tumours and adjacent structures.

A variety of tumours may arise in the pineal region; accurate diagnosis is important in the selection of treatment and prognosis. A retrospective analysis of the MRI studies of 25 patients with pathologically proven pineal region tumours was performed, focused on the relationship between the tumour and neighbouring structures. Compression of the tectal plate was classified as expansive or invasive, and compression of the corpus callosum as inferior, anterior or posterior. In 10 of the 14 patients (71%) with germ cell tumours tectal compression was of the invasive type; 8 patients (57%) had multiple tumours and in 13 (93%) the tumor margins were irregular. Teratomas were readily diagnosed because of characteristic heterogeneous signal intensity. Pineal cell tumours were differentiated from germ cell tumours by their rounded shape, solid nature, sharp margins, and expansive type of tectal compression. Meningiomas were characterised by their falcotentorial attachments, posterior callosal compression, and a low-intensity rim on T2-weighted images. Gd-DTPA injection enabled clear demonstration of the site and extent of tumour spread and was useful in differentiating cystic and solid components. The appearances described, while not pathognomonic, are helpful in the differential diagnosis of pineal region tumours, and valuable in planning appropriate treatment.

Adolescent↗
PubMed1983

Thalamic inputs to identified commissural neurons in the monkey somatic sensory cortex.

Commissurally projecting neurons were identified in the monkey first somatic sensory area (SI) by the retrograde axonal transport of horseradish peroxidase (HRP) injected into the contralateral cortex. Neurons identified in this way have large pyramidal somata primarily in layer IIIB of the SI area. Their basal dendrites lie within the terminal plexus of thalamocortical afferents. Electron microscopy was used to examine the synaptic relations of the labelled commissural cells, in particular to determine whether they receive monosynaptic thalamic connections. To do this, retrogradely labelled commissural cells and Golgi-impregnated large pyramidal neurons from layer IIIB were examined ultrastructurally in material in which thalamocortical terminals were degenerating due to a prior lesion of the thalamus. In a significant number of cases degenerating terminals were found to make synapses on the spines or shafts of labelled dendrites. Injections of HRP into SI or into the white matter adjacent to the corpus callosum labelled callosal axons and terminals in the opposite SI. These axons terminated mainly near the somata of the layer IIIB pyramidal cells. Some of their terminals were found to synapse with dendrites receiving synaptic contacts from thalamocortical axon terminals.

Animals↗
PubMedDate not supplied

Transcallosal modulation of a focus of maximal activity in the motor cortex.

Evoked potentials were recorded from 170 symmetrical points of the motor cortex in acute experiments on 10 cats anesthetized with chloralose and pentobarbital. Callosal influences on the focus of maximal activity (FMA) were studied during bilateral and unilateral electrical stimulation of the sciatic nerves at different strengths. During weak stimulation division of the corpus callosum was shown to broaden the FMA, but during strong stimulation the FMA was narrowed. It is suggested that transcallosal modulation in the intact brain leads to clearer demarcation of the FMA in the motor cortex and also increases the differences between FMAs arising during stimulation at different strengths.

Animals↗
PubMedDate not supplied

Modules of cortical neurons and their "self-assembly".

The data we have by now accumulated on the cytoarchitectonics of the cerebral cortex, as well as published data, suggest that some of the neurons are structurally combined into compact clusters (ensembles, blocks), and that the majority of them participate in the construction of these clusters by directing the terminal branches of their axons to them. The collaterals of projection, associative, and callosal nerve cells, as well as the axons of interneurons which accomplish local interneuronal closures, can combine individual elements of the ensembles into a unified morphofunctional system. The collaterals of the axons of a block of neurons spread divergently to neurons disposed along the perimeter, while the axons of the latter converge reciprocally to the neurons of the cluster, forming a maximum (focus) of the arborization of the axonal terminals there; this makes it possible actively to isolate modules of nerve cells by accomplishing their self-assembly.

Animals↗
PubMed1988

Corpus callosotomy in the treatment of secondary generalizing intractable epilepsy.

Over the past 5 years 9 patients underwent partial or complete corpus callosotomy for treatment of medically intractable epileptic seizures. A beneficial effect of the procedure was observed in 8 patients. Criteria for performance of the procedure included CT evidence of unilateral cerebral damage and non-localized epileptic foci in that hemisphere with secondary spread to the uninvolved side. The best results were obtained in atonic seizures. Long-term side effects were minor. The procedure is recommended in those patients with medically uncontrolled atonic or secondary generalized motor seizures in whom the corpus callosum is thought to mediate the spread of epileptic activity from a damaged cerebral hemisphere. Side effects are minimized by staging of the callosal section. If a partial callosotomy was beneficial, complete section can then be avoided.

Adolescent↗
PubMed1986

Massive traumatic haematoma of the corpus callosum.

Five unusual cases with massive haematoma of the corpus callosum caused by blunt head trauma are presented. Aside from the callosal haematomas, intraventricular and subarachnoid haemorrhages or small haemorrhagic foci in the basal ganglia or thalamus were common concomitant lesions on the computerized tomographic (CT) scan. The sites of the impacts were the frontal and occipital areas which were close to the midline and above the level of the corpus callosum. Severe and diffuse brain dysfunction was suggested by the severity of the Glasgow coma score (GCS) and the abnormality on multimodality evoked potentials. An intensive medical treatment such as barbiturate could be promising since a direct surgical approach was dubious because of additional damage to the severely injured brain.

Adult↗
PubMed1992

The venous vascularization of the corpus callosum in man.

The vascularization of the corpus callosum in Man is studied in 20 brains. Their vascular system is injected with Indian ink and gelatin. The corpus callosum is drained by callosal veins and callosocingulate veins towards the deep venous system of the brain. Most of these veins run downwards and join together at the central level of the corpus callosum. They then form the subependymal veins, which form the septal veins and the medial atrial vein. All these vessels are tributaries of the internal cerebral veins.

Adult↗
PubMed1994

One hundred years of neuropsychology in Japan: retrospect and prospect.

The development of neuropsychology in Japan since the end of the 19th century will be outlined, including a number of pioneering works that gave a scientific basis to contemporary Japanese neuropsychology. The activities of societies/associations of related disciplines as well as the educational systems of clinical and experimental neuropsychology, which represents in Japan an interdisciplinary field, will be described. After national and international activities are mentioned, a review of significant Japanese contributions to main topics in neuropsychology will be given in some detail: dementia, memory disorders, frontal lobe syndromes, aphasia-alexia-agraphia, callosal syndromes, and specific right hemisphere syndromes. The issues of these interdisciplinary scientific investigations have found application in language and cognitive disabilities of brain-damaged patients, as well as evaluation of medical treatments and comedical rehabilitational effects, care, and counseling. Finally, some comments will be presented on possible and desirable developments of Japanese neuropsychology in the future.

History, 19th Century↗
PubMed1994

Familial mitochondrial encephalopathy with fetal ultrasonographic ventriculomegaly and intracerebral calcifications.

In two sibs antenatal ultrasonography revealed identical intracranial calcification, ventricular widening and microcephaly. The first pregnancy was artificially terminated at 19 weeks. Post-mortem examination of the brain revealed destructive calcification and extracerebral neuronal heterotopia. The second sib went to term but died 48 h after birth from irreversible lactic acidosis. Autopsy showed extensive encephalopathy with cavitation and calcification in the cerebral hemispheres, polymicrogyria, multiple neuronal heterotopia, partial callosal dysgenesis, and severe Leigh syndrome, together forming a continuum of early and late brain disruption. Mitochondrial respiratory chain abnormalities, mainly affecting complexes I and IV, and deficiency of pyruvate dehydrogenase complex were detected in skeletal muscle and in liver. A normal functioning of the respiratory chain was found in the fibroblasts. Analysis of mtDNA from muscle, liver and blood revealed normal amounts of intact mtDNA without any of the known point mutations associated with MELAS, MERRF or Leigh syndromes. The early fetal disruption and necrotic changes in the brains of sibs indicate a specific genetically determined disorder which affects neuronal migration, a finding not previously associated with respiratory chain disorders. The present disorder may mimic antenatal congenital infectious encephalopathy because of the combined finding of microcephaly and destructive intracerebral calcification.

Brain↗
PubMed1993

Lipoma of the corpus callosum in a neonate: sonographic evaluation.

Lipomas of the corpus callosum are benign neoplasms which are rarely diagnosed in pediatric patients. In infants they are congenital lesions consisting of collections of adipose tissue; their etiology is unclear. We describe a case of callosal lipoma discovered by sonography in a 2-day-old neonate.

Brain Neoplasms↗
PubMed1993

Tuberous sclerosis associated with pachygyria. CT findings.

The case is presented of a 1.5-year-old with the typical CT features of tuberous sclerosis and pachygyria, in combination. Tuberous sclerosis was evidenced by multiple subependymal calcifications, and pachygyria by the relevant CT appearances. Periventricular heterotopia and total callosal agenesis were associated findings. The findings in this patient convincingly suggest a close relationship between tuberous sclerosis and pachygyria, although the case is the first to be reported in the literature.

Brain↗