Growth dynamics and morphology of regenerating optic fibers in tectum are altered by injury conditions: an in vivo imaging study in goldfish

The dynamic behavior of axons in systems that normally regenerate may provide clues for promoting regeneration in humans. When the optic nerve is severed in adult goldfish, all axons regenerate back to the tectum to reestablish accurate connections. In adult mammals, regeneration can be induced in optic and other axons but typically few fibers regrow and only for short distances. These conditions were mimicked in the adult goldfish by surgically deflecting 10-20% of optic fibers from one tectum into the opposite tectum which was denervated of all other optic fibers by removing its corresponding eye. At 21-63 days, DiI was microinjected into retina to label a few fibers and the fibers were visualized in the living fish for up to 5-7 h. The dynamic behavior and morphology of these regenerating deflected fibers were analyzed and compared to those regenerating following optic nerve crush. At 3-4 weeks, deflected fibers were found to form more branches and to maintain many more branches than crushed fibers. Although both deflected and crushed fibers exhibited stochastic growth and retraction, deflected fibers spent more time growing but grew for less distance. At 2 months, both deflected and crushed fibers became much more stable. These results show that the morphology and behavior of fibers regenerating into the same target tissue can be substantially altered by the injury conditions, that is, they show state-dependent plasticity. The morphology and behavior of the deflected fibers suggest they were impaired in their capacity to grow to their correct targets.     

Seeing voices: High-density electrical mapping and source-analysis of the multisensory mismatch negativity evoked during the McGurk illusion

Seeing a speaker's facial articulatory gestures powerfully affects speech perception, helping us overcome noisy acoustical environments. One particularly dramatic illustration of visual influences on speech perception is the "McGurk illusion", where dubbing an auditory phoneme onto video of an incongruent articulatory movement can often lead to illusory auditory percepts. This illusion is so strong that even in the absence of any real change in auditory stimulation, it activates the automatic auditory change-detection system, as indexed by the mismatch negativity (MMN) component of the auditory event-related potential (ERP). We investigated the putative left hemispheric dominance of McGurk-MMN using high-density ERPs in an oddball paradigm. Topographic mapping of the initial McGurk-MMN response showed a highly lateralized left hemisphere distribution, beginning at 175 ms. Subsequently, scalp activity was also observed over bilateral fronto-central scalp with a maximal amplitude at approximately 290 ms, suggesting later recruitment of right temporal cortices. Strong left hemisphere dominance was again observed during the last phase of the McGurk-MMN waveform (350-400 ms). Source analysis indicated bilateral sources in the temporal lobe just posterior to primary auditory cortex. While a single source in the right superior temporal gyrus (STG) accounted for the right hemisphere activity, two separate sources were required, one in the left transverse gyrus and the other in STG, to account for left hemisphere activity. These findings support the notion that visually driven multisensory illusory phonetic percepts produce an auditory-MMN cortical response and that left hemisphere temporal cortex plays a crucial role in this process.     

Risk factors for late-onset seizures related to cerebral contusions in adults with a moderate traumatic brain injury

Objectives

This prospective study compares the characteristics of patients with a moderately severe traumatic brain injury (TBI) and cerebral contusions who develop late-onset seizures to those who do not.

Patients and methods

Thirty-nine adult TBI patients with cerebral contusions, who did not need a neurosurgical treatment, could be followed up for more than 3 years. Fourteen patients developed seizures during that period and 25 did not. The Glasgow Coma Scale (GCS) score on admission and the modified Rankin (mR) score on discharge from the hospital, the computed tomography (CT) and/or magnetic resonance imaging (MRI) findings, the electroencephalogram (EEG) patterns as well as the vascular and habit risk factors were compared between both groups.

Results

The mean GCS and mR scores were moderately severe and comparable between both groups. Early-onset seizures represented 21.4%. The overall seizure recurrence was 85.7% after treatment with carbamazepine or valproate sodium. Still 3 patients did not remain seizure-free after addition of another antiepileptic drug. The average number of brain contusions on CT/MRI was approximately the same. Vascular risk factors and alcohol abuse were more observed in the seizure patients. Abnormal EEG findings on discharge from the hospital were significantly more frequent in the patients who developed late-onset seizures afterward (P < 0.05).

Conclusions

Seizures after non-complicated cerebral contusions are difficult to treat. Vascular risk factors and alcohol abuse may also predispose to their occurrence. The EEG findings after the TBI are highly predictive.     

The biological and electrical trade-offs related to the thickness of conducting polymers for neural applications

Poly(3,4-ethylenedioxythiophene) (PEDOT) films have attracted substantial interest as coatings for platinum neuroprosthetic electrodes due to their excellent chemical stability and electrical properties. This study systematically examined PEDOT coatings formed with different amounts of charge and dopant ions, and investigated the combination of surface characteristics that were optimal for neural cell interactions. PEDOT samples were fabricated by varying the electrodeposition charge from 0.05 to 1 C cm⁻². Samples were doped with either poly(styrenesulfonate), tosylate (pTS) or perchlorate. Scanning electron micrographs revealed that both thickness and nodularity increased as the charge used to produce the sample was increased, and larger dopants produced smoother films across all thicknesses. X-ray photoelectron spectroscopy confirmed that the amount of charge directly corresponded to the thickness and amount of dopant in the samples. Additionally, with increased thickness and nodularity, the electrochemical properties of all PEDOT coatings improved. However, neural cell adhesion and outgrowth assays revealed that there is a direct biological tradeoff related to the thickness and nodularity. Cell attachment, growth and differentiation was poorer on the thicker, rougher samples, but thin, less nodular PEDOT films exhibited significant improvements over bare platinum. PEDOT/pTS fabricated with a charge density of <0.1 C cm⁻² provided superior electrochemical and biological properties over conventional platinum electrodes and would be the most suitable conducting polymer for neural interface applications.     

Osteoclast resorption of beta-tricalcium phosphate controlled by surface architecture

A resorbable bone graft substitute should mimic native bone in its capacity to support bone formation and be remodeled by osteoclasts (OCl) or other multinucleated cells such as foreign body giant cells (FBGC). We hypothesize that by changing the scale of surface architecture of beta-tricalcium phosphate (TCP), cellular resorption can be influenced. CD14⁺ monocyte precursors were isolated from human peripheral blood (n = 4 independent donors) and differentiated into OCl or FBGC on the surface of TCP discs comprising either submicron- or micron-scale surface topographical features (TCPs and TCPb, respectively). On submicrostructured TCPs, OCl survived, fused, differentiated, and extensively resorbed the substrate; however, on microstructured TCPb, OCl survival, TRAP activation, and fusion were attenuated. Importantly, no resorption was observed on microstructured TCPb. By confocal microscopy, OCl formed on TCPs contained numerous actin rings allowing for resorption, but not on TCPb. In comparison, FBGC could not resorb either TCP material, suggesting that osteoclast-specific machinery is necessary to resorb TCP. By tuning surface architecture, it appears possible to control osteoclast resorption of calcium phosphate. This approach presents a useful strategy in the design of resorbable bone graft substitutes.     

CT引导下经皮肺活检48例临床分析

目的：探讨肺部外周性病变的诊断准确性。方法：对痰细胞学阴性纤支镜不能确诊的48例肺部外周性病变患者，在胸部CT扫描定位下，用20G活检针经皮肺穿刺活检取材，行病理学诊断。结果：48例患者共行穿刺53次，阳性（43／48）占89．6％，阴性（5／48）占10．4％，经手术后病理、临床证实，其恶性病变诊断正确率93．3％（28／30），良性病变诊断正确率83．3％（15／18），误诊率10．4％。术后小量咯血2例，未发生气胸及死亡病例。结论：以CT引导下经皮肺活检是一种安全、有效的检查手段，对肺部周围性病变具有较高的诊断价值。     

Distribution of neurons related to a hindlimb as opposed to forelimb movement in the monkey premotor cortex

Summary Single cell recordings were made from the premotor cortex (lateral part of area 6) of a monkey trained to perform either a distal hindlimb or forelimb movement separately. Out of 175 movement-related neurons, 59 neurons showed modulation of activity only prior to the hindlimb movement, and the majority of them was distributed in a focal region around the superior precentral sulcus, several mm posteromedial to the genu of the arcuate sulcus. The hindlimb focus was separate from a focal region for forelimb movement-related neurons, which lay immediately posterior to the genu of the arcuate sulcus.Supported in part by Ministry of Education, Science and Culture of Japan (grant 58106001 and 58570046)     

Innovative surfaces and alloys for dental implants: What about biointerface-safety concerns?

ObjectivesThe present review article aimed to discuss the recent technologies employed for the development of dental implants, mainly regarding innovative surface treatments and alternative alloys, emphasizing the bio-tribocorrosion processes.MethodsAn electronic search applying specific MeSH terms was carried out in PubMed and Google Scholar databases to collect data until August 2021, considering basic, pre-clinical, clinical and review studies. The relevant articles (n = 111), focused on innovative surface treatments for dental implants and their potential undesirable biological effects, were selected and explored.ResultsNovel texturization methodologies for dental implants clearly provided superficial and structural atomic alterations in micro- and nanoscale, promoting different mechanical-chemical interactions when applied in the clinical set. Some particulate metals released from implant surfaces, their degradation products and/or contaminants exhibited local and systemic reactions after implant installation and osseointegration, contributing to unexpected treatment drawbacks and adverse effects. Therefore, there is an urgent need for development of pre-clinical and clinical platforms for screening dental implant devices, to predict the biointerface reactions as early as possible during the development phases.SignificanceModern surface treatments and innovative alloys developed for dental implants are not completely understood regarding their integrity during long-term clinical function, especially when considering the bio-tribocorrosion process. From this review, it is possible to assume that degradation and contamination of dental surfaces might be associated within peri-implant inflammation and cumulative long-lasting systemic toxicity. The in-depth comprehension of the biointerface modifications on these novel surface treatments might preclude unnecessary expenses and postoperative complications involving osseointegration failures.     

The projection of different retinal ganglion cell classes to the dorsal lateral geniculate nucleus in the hooded rat

Summary The morphology of retinal ganglion cells which project to different parts of the dorsal lateral geniculate nucleus (DLG) in the hooded rat has been investigated. Small amounts of a retrograde tracer (horseradish peroxidase) were injected into the DLG, then labelled retinal ganglion cells were examined in retinal wholemounts. After injections into different parts of the DLG, differences were noted in the size, morphology and retinal distribution of labelled retinal ganglion cells. Specifically, after injections into the antero-ventral part of the DLG labelled retinal ganglion cells were spread sparsely across the retina, had large cell somas, and many were identified with Class I or Class III morphology. After injections into the postero-dorsal part of the DLG, labelled cells were more densely packed, had smaller somas, and more were identified with Class IIa and Class III morphology. The density of labelled cells was estimated to be no more than 37% of the total retinal ganglion cell density at any retinal position examined. These results show that in the rat, as in other species such as the cat or monkey, the terminals of different classes of retinal ganglion cells are segregated within different subdivisions of the DLG. However, unlike these other species, only a minority of the total retinal ganglion cell population projects to the DLG.