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At least 37 records · Page 2Linked to original sources
PubMed2026

Faster N1 latency in response to homeostatic-like plasticity of PREPs is impaired during pain: A randomized-placebo capsaicin-pain study.

INTRODUCTION: Homeostatic-like plasticity (HP-like) stabilizes cortical excitability through long-term potentiation and depression-like mechanisms. The efficacy of homeostatic regulation in the corticomotor system is impaired during pain, which may have functional relevance for chronic pain. This study investigated whether a cortical HP-like response could be assessed by nociceptive stimulation, and if such response was impaired by experimental tonic pain. METHODS: Twenty-eight healthy participants completed placebo and capsaicin sessions, with 11 sham controls for time and design. HP-like plasticity was induced with two blocks of anodal tDCS over the primary motor cortex. The N1 (TP7) and N2P2 (Cz) components of electrically induced pain-related evoked potentials (PREPs) were assessed from the volar forearm before and after patch application, and again immediately and 20 min after HP-like induction. An HP-like response was defined by PREP decrease after induction, and further normalization to baseline. RESULTS: Anodal tDCS did not induce an HP-like regulation of PREP amplitudes. Interestingly, an HP-like response was observed as a fastening of N1 latency after HP-like induction, which returned to baseline values after 20 min. The latter effect was impaired during capsaicin-induced pain, where N1 was slower. The N2P2 component showed habituation over time in all sessions. CONCLUSION: This is the first study that investigates the HP-like regulation of nociceptive-evoked responses. An HP-like response was observed as a shortening of N1 latency, suggesting that early nociceptive processing may be susceptible to homeostatic regulation. In contrast, the later component, N2P2, showed habituation over time, which prevented evaluation of HP-like effects.

Humans↗
PubMed2026

Genome-Wide and Rare Variant Association Studies of Amblyopia in Admixed American and African Ancestry Groups.

OBJECTIVE: To identify genetic variants associated with amblyopia in African (AFR) and Admixed American (AMR) ancestry groups, expanding on previous studies conducted in European ancestry. DESIGN: Retrospective ancestry-stratified genome-wide association study (GWAS) and gene-level rare variant association study (RVAS). PARTICIPANTS: Participants in the All of Us Research Program from AFR and AMR ancestry groups who had whole-genome sequencing available. Cases and controls were distinguished based on the presence of International Classification of Diseases 9/10/SNOMED diagnosis codes for amblyopia in electronic health records. This yielded ancestry-stratified subsets of 269 cases and 71 585 controls of AMR ancestry and 366 cases and 79 460 controls of AFR ancestry. METHODS: Stratified logistic regression models were adjusted for age, biological sex, and the top 10 principal components of genomic ancestry. GWAS was limited to common variants (minor allele frequency &#x2265;1%), and RVAS was limited to rare variants with coding sequence-altering effects (minor allele frequency >1%, exonic only, excluding synonymous variants) aggregated at the gene level using the SKAT algorithm. Downstream analyses of the significant variants were performed using KEGG and GO pathway analysis and STRING database queries for protein-protein interactions and gene-gene interactions. MAIN OUTCOME MEASURES: Single-nucleotide polymorphisms were determined to have genome-wide significance if P < 5e-8 in the GWAS, and genes were determined to have significant association with amblyopia in the RVAS if P < 8.0 &#xd7; 10-4. RESULTS: In the AMR GWAS, 245 unique single-nucleotide polymorphisms mapping to 97 distinct loci were identified, notably within neurodevelopmental and axonal guidance genes, including ROBO1, SEMA4B, PTPRD, NRXN1, and CAMK2D. The AFR GWAS identified 11 significant variants corresponding to 6 loci mapping primarily to long noncoding RNAs and pseudogenes. The AMR RVAS identified 15 genes, including axonal transport genes (KIF1B and KIF7) and growth factor signaling genes (EGF, ERBIN, and AKAP17A). The AFR RVAS identified a single gene, DLG2, which encodes the postsynaptic protein PSD-93, which promotes the closure of the sensitive period of neuroplasticity for vision in early childhood. CONCLUSIONS: Genetic risk architectures for amblyopia differ across ancestries but fundamentally converge on neurodevelopmental signaling, cortical synapse assembly, and sensitive period plasticity rather than ocular structural dynamics. FINANCIAL DISCLOSURE(S): The authors have no proprietary or commercial interest in any materials discussed in this article.

Amblyopia↗
PubMed1975

Neural plasticity in visual cortex of adult cats after exposure to visual patterns.

Over a period of 2 weeks, adult cats were twice a day exposed for 1 hour to a visual environment consisting only of vertical stripes and for the rest of the time were kept in darkness. Subsequent investigation of the striate cortex showed a decrease in the number of neurons sensitive to orientations around the vertical relative to those sensitive to horizontal orientations. This indicates that plasticity of functional properties of the cortical neuronal network still exists in adult animals.

Animals↗
PubMed1978

Facilitatory and inhibitory effects of electrochemical stimulation of the amygdala on the release of luteinizing hormone.

The effect of amygdaloid stimulation on the release of luteinizing hormone (LH) was studied in unanesthetized, unrestrained rats. Electrochemical stimulation (anodic D.C.) was applied at 11.30 h through stainless steel electrodes chronically implanted into different amygdaloid nuclei; medial (Men.), cortical (Con.), central (Cn.), or basolateral (Bln.). A plastic cannula inserted into the jugular vein was used for obtaining blood samples at different times of the experimental procedure. In rats on the day of proestrus, stimulation (100 micronA/30 sec) in the Bln. resulted in blockade of spontaneous ovulation and of the preovulatory LH release and that in the Cn. produced a delay in the hormone discharge. On the contrary, stimulation in the Men. was effective in advancing the time of the normal LH surge, while no change of the normal pattern occurred from the Con. Stimulation (100 micronA/60 sec) of ovariectomized estrogen primed rats applied in the Men. or the Con. induced LH release, while that in the Bln. or the Cn. had no effect. The release of LH by Men. stimulation and the blocking effect of Bln. showed a close relationship with the amount of current delivered. Lower thresholds were required for inhibition than for activation. The release of LH induced by stimulation in the Men. of ovariectomized estrogen primed rats occurred at the same time of the day whether the stimulus was applied at 8.30 h, 11.30 h or 14.00 h, indicating a modulatory effect of the amygdala. No changes in serum LH concentration were observed after stimulation of the Men. of castrated estrogen primed male rats or in the Bln. of ovariectomized non-primed rats. The present results indicate that the amygdala exerts a dual effect on the release of LH, the Bln. being inhibitory and the Men. and Con. facilitatory.

Amygdala↗
PubMed1976

Neuroplasticity in the rearrangement of olfactory tract fibers after neonatal transection in hamsters.

Olfactory bulb efferent axons run caudally in the lateral olfactory tract (LOT) to end in a broad cortical field in the ventral forebrain. Principles governing the plastic rearrangement of this fiber population after early lesions were probed by cutting the tract in hamster pups and studying the distribution of surviving olfactory bulb projections in adulthood using silver and autoradiographic techniques. The spatial pattern of rearrangement proved to depend on the extent of the cut and also the age at which it was made. For example, after complete LOT section at seven days of age no bulb efferents appeared distal to the cut but the proximal projection increased in laminar thickness and spread laterally and medially beyond its normal cytoarchitectonic boundaries. This spread was less pronounced in animals with earlier or later lesions. After transection of only part of the LOT fibers at seven days of age the proximal input was similarly increased. Just distal to the transection, uncut fibers sprouted collaterals to fill the terminal sites vacated as a result of the lesion. In these cases, however, the farthest distal parts of the projection field lost their normal innervation. In a tentative interpretation of these data it is proposed that developing LOT fibers tend to conserve their total amount of axonal arbor. That is, when distal branches are pruned off surgically, the axon compensates by producing extra proximal branches. When an overabundance of proximal collaterals are produced in axons that have not been surgically pruned the growth of more distal axonal branches is stunted in compensation.

Animals↗
PubMed2025

Druggable genome CRISPRi screen in 3D hydrogels reveals regulators of cortactin-driven actin remodeling in invading glioblastoma cells.

To identify new therapeutic targets that limit glioblastoma (GBM) invasion, we applied druggable-genome CRISPR screens to patient-derived GBM cells in micro-dissectible biomimetic 3D hydrogel platforms that permit separation and independent analysis of core vs. invasive fractions. We identified 12 targets whose suppression limited invasion, of which ACP1 (LMW-PTP) and Aurora Kinase B (AURKB) were validated in neurosphere assays. Proximity labeling analysis identified cortactin as an ACP1-AURKB link, as cortactin undergoes serine phosphorylation by AURKB and tyrosine dephosphorylation by ACP1. Suppression of ACP1 or AURKB in culture and in vivo shifted the balance of cortactin phosphorylation in GBM and reduced actin polymerization and actin-cortactin co-localization. Additional biophysical analysis implicated AURKB in GBM cell adhesion and cortical stiffness, and ACP1 in resistance to mechanical stress and shape plasticity needed for 3D migration. These findings reveal a novel targetable axis that balances kinase and phosphatase activities to regulate actin polymerization during GBM invasion.

CRISPR↗
PubMed1976

Response plasticity in hamster olfactory bulb: peripheral and central processes.

It is a well-established fact that prolonged odor stimulation leads to marked sensory adaptation. This study demonstrates comparable electrophysiological phenomena occurring at the level of the olfactory receptor and at more central olfactory structures. Recordings of overall receptor response and of olfactory bulb unit responses were made during repeated odor stimulation. During the course of a single, continuous odor presentation response decrements were seen in the EOG (at the olfactory receptors) and were mirrored at the mitral cell layer of the bulb. When brief periods without stimulation were introduced between such odor presentations, receptor responsiveness rebounded to its original level, but mitral cell responses did not. On the basis of this dissociation it is suggested that the pattern of response decrement within the bulb represents a case of stimulus-specific habituation in a simple cortical subsystem and is well worth future investigation as a model of neural plasticity. Surgical disconnection of the olfactory bulb from one or more of its centrifugal inputs results in hyperactive, hyperresponsive mitral cells, which habituate more rapidly and show longer recovery times than do those in the intact bulb. In addition, the synchronization of such units to the inhalation cycle is markedly reduced as compared with normal preparations. These facts together suggest that the habituation of mitral cell activity does not depend on centrifugal inputs, although one or more of such inputs act indirectly in an inhibitory fashion to modulate and tune mitral cell response characteristics.

Adaptation, Physiological↗
PubMed1978

Histomorphometric analysis of normal bone from the iliac crest.

Bone specimens from a standardized area of the iliac crest were obtained at autopsy in 105 individuals after sudden unexpected death and at biopsy in 30 living volunteers. Seven micron thick sections of the plastic embedded undecalcified material were produced and stained. The amount of cancellous and cortical bone and the parameters attached to description of bone remodelling were determined by point counting and simple measurements, in order to establish normal mean values and range in a Danish population. A decrease in the amount of bone, trabecular as well as cortical, was found with increasing age in both males and females. The extent, volume and width of osteoid seams and the osteoclastic resorption were found to be age-independent. The osteoclastic resorption in cortical bone in males decreased, however, with increasing age. The reported values are of the greatest importance for the use of histomorphometric analysis of bone biopsies as a diagnostic tool in metabolic bone diseases. It is stressed, however, that supplementary information of the dynamic aspects of the bone remodelling would be necessary for the understanding of the pathogenesis of bone changes. Such information might be obtained by using tetracyline double labelling.

Adolescent↗
PubMed1978

The juxtaglomerular apparatus in a human kidney with polar artery stenosis.

Juxtaglomerular apparatuses (JGA) of a human kidney with stenosis of a polar artery from a hypertensive 18-year-old male patient were studied qualitatively and quantitatively on 2 mu thick serial sections from plastic embedded renal tissue. 11 JGA from juxtamedullary and 9 JGA from subcapsular cortical zones were photographed serially, the copies taped together and the cells and relationships within the JGA studied. On the copies the lenght of contact between the different juxtaglomerular structures and the basement membrane of the macula densa was measured. Futhermore we calculated the areas of surface contact and the macula densa basal area. In the juxtamedullary JGA affected by the polar artery stenosis all Goormaghtigh cells were transformed into epitheloid cells and the Goormaghtigh cell field was significantly larger than in the JGA of the subcapsular cortex, which obviously had been exposed to the systemic hypertension. The macula densa basal area was significantly greater in the juxtamedullary JGA than in the subcapsular JGA, but neither of these differed significantly from the macula densa in the normal JGA reported previously.

Adolescent↗
PubMed1979

Neuronal mechanisms of conitioned placing reactions in cats.

Neuronal correlates of conditioned placing reaction of cat’s forepaw were studied. The conditioned reaction evoking by tactile stimulation of the paw’s ventral side had the same motor pattern, consisting mainly in successive flexion and extension of elbow joint, as the placing reaction evoked by paw’s dorsal side stimulation in naive animals. The activity of single neurons from the m. biceps representation area in pericruciate motor cortex and VL thalamic nucleus was recorded. As a result of learning the excitatory response of cortical neurons to paw’s ventral side stimulation in 20-50 ms post-stimulus interval was 2-2.5 times more than the response to the same stimulation in naive cats. This short-latency increase of response was not accompanied by modifications of sensory inflow to the motor cortex or movement related afferentation changes arriving from VL nucleus. There were no marked differences in excitability of cortical neurons of naive and trained animals as well. The results suggest a functional plasticity of the neuronal net in the motor cortex, consisting of a change in the efficiency of connections between neurons receiving sensory determined afferent excitation and the functional groups of neurons controlling the contraction of different muscles.

Animals↗
PubMed1979

Plasticity: the mirror of experience.

A simple avoidance training procedure during early development produces massive neural traces in visual and somatic cortices of kittens reared in a normal environment. A preponderance of cells in these areas had response preferences for the stimuli used during training. Furthermore, some of these cells exhibited properties never found in normal animals not receiving such training. It appears that, even in an environment in which many other stimuli are present, some early experiences powerfully affect brain development and the way in which other experiences exert their effect.

Animals↗
PubMed1975

Serotonin nerve terminals in adult rat neocortex.

Axonal processes which take up and retain exogenous tritiated serotonin ([3H]5-HT) have been demonstrated in the fronto-parietal cortex of adult rats, by means of high resolution radioautography. Prolonged topical superfusion with relatively high concentrations of ([3H]5-HT allowed detection of a maximal number of axonal reactions in the upper 3 layers of cortex. Comparison of results obtained from normal rats and animals pretreated with 6-hydroxydopamine or bearing midbrain raphe lesions established the specificity of this labeling. All reactive axons seemed to arise from the serotonin nerve cell bodies in groups B7 and B8 of Dahlström and Fuxe15. In electron microscope radioautographs, the serotonin fibers appeared as tenuous, naked axonal processes (0.1-0.5 mum in diameter) exhibiting small enlargements (0.7 mum in mean diameter) spaced at frequent intervals (1-3 mum). These boutons contained occasional mitochondria, small, round, agranular 'synaptic' vesicles and large granular vesicles. With axons, [3H]5-HT was concentrated in the boutons, and to a much lesser extent in connecting segments. This reactive pattern resembled that revealed by the fluorescence technique for endogenous serotonin. Preferential accumulations of the tracer by mitochondria and vesicular organelles indicated that these elements could sequester exogenous serotonin. Large granular vesicles were not necessarily visible in random thin sections of the labeled varicosities, and thus could not serve as the unique criterion for electron microscopic identification of 5-HT terminals. Moreover, these organelles are known to be present in other types of nerve endings. Topometric analysis of serial thin sections nevertheless demonstrated that large granular vesicles were potentially detectable in every 5-HT containing bouton, and also enabled extrapolation of their average number at 7 per varicosity. This low number makes it unlikely that large granular vesicles primarily represent storage sites. They could rather serve as a carrier for particle-bound enzymes essential to the local metabolism of serotonin or its precursors. A very small fraction of the serotonin varicosities exhibited the membrane differentiations of typical synaptic terminals. Extensive sampling in serial thin sections revealed junctional complexes in only 5% of labeled boutons, as opposed to 50% of unlabeled nerve endings in the surrounding neuropil. The data do not preclude the possibility that other monoaminergic neurons also share similar characteristics. It is probable that endogenous serotonin can be liberated from all axonal varicosities including those lacking strictu senso synaptic relationships. The overall configuration and ultrastructural features of cortical serotonin fibers suggest intrinsic dynamic properties which could assume particular significance in terms of function, plasticity and regrowth.

Animals↗
PubMed1977

[The influence of the countersink geometry on the cortical screw force (author's transl)].

In vitro examinations on deformation and relaxation were carried out on cortical countersink of different geometry under a compression load of up to 2000 N through a screw head. Conical countersink showed plastic deformations of an average of 1300 N whereas with spherical countersink they did not occur at the same load. After reaching the load of 2000 N and keeping the deformation constant we saw a significantly stronger reduction of force with the conical countersink then with the spherical type. As far as fracture fixation is concerned a smaller postoperative reduction of screw force can be expected if applying a cortical screw with a spherical head in a spherical countersink.

Aged↗
PubMedDate not supplied

[Cortico-subcortical systems of conditioned reflex activity].

Experimental data are presented on dynamic rearrangment of corticofugal influences on subcortical structures during conditioning and conditioned performance, as well as data on the transition of diffusive influences, to selective ones. The mechanisms of plastic rearrangment of subcortical influences in the course of consolidation of the conditioned reflex are discussed on the basis of cortical-reticular and cortical-striate interactions. The significance of subcortical interactions in the integrative brain activity and in the organization of behaviour is discussed. Facts are presented on synchronization of several rhythms in rhythmical activity in the strio-thalamo-cortical system in the process of achievement of conditioned reflexes.

Brain↗
PubMed1976

Stable and plastic unit discharge patterns during behavioral generalization.

A movable microelectrode was implanted in adult cats trained to respond differentially to two different frequencies of light flicker. Unit responses were recorded along cortical and thalamic trajectories. The late components of the poststimulus response of 29% of the cells examined showed statistically significant differences when data from different behavioral outcomes to the same neutral generalization stimulus were compared.

Action Potentials↗
PubMed1979

Acute plastic bowing fractures of the fibula.

Two cases of acute plastic bowing fractures of the fibula are described. A brief description of the mechanism of bone deformation under stress and the pathological cortical microfractures involved in bowing fractures is given.

Child, Preschool↗
PubMed1979

Comparative bone morphometric analysis of mandibles and iliac crests.

A comparative analysis of bone mass in the mandible and the iliac crest has been carried out in autopsy specimens from 30 subjects aged 23-84 years. Microradiograms of standardized 100-micrometer-thick sections of the undemineralized plastic embedded material from the two locations were used for quantitation. The following measurements were carried out by electronic point-counting: 1) the percentage of cortical bone mass in the subperiosteal and subendosteal layers, 2) mean cortical width, and 3) the percentage of trabecular bone mass in the iliac crest. Positive correlations were found in the expressions of bone mass within the mandible; the values were significantly higher in the 200-micrometer-thick subperiosteal layer than in the remaining part of the mandibular cortex. Only a poor or no correlation was found in the expressions of bone mass from the two sites. The investigation, therefore, shows that bone mass and cortical width in the mandible cannot be predicted from a biopsy from the iliac crest. This finding may partly be due to different age-dependent functional changes of the two bones.

Adult↗