Physiology and morphology of callosal projection neurons in mouse

In the mammalian neocortex, the corpus callosum serves as the major source of interhemispheric communication, composed of axons from callosal neurons located in supragranular (II/III) and infragranular (V/VI) layers. We sought to characterize the physiology and morphology of supragranular and infragranular callosal neurons in mice using retrograde tracers and whole-cell patch clamp recordings. Whole-cell patch clamp recordings were made from retrogradely labeled callosal neurons following unilateral injection of fluorescent latex microspheres in the contralateral sensory-motor cortex. Following recordings and biocytin dialysis, labeled neurons were reconstructed using computer-assisted camera lucida (Neurolucida) for morphological analyses. Whole-cell recordings revealed that callosal neurons in both supra- and infragranular layers display very similar intrinsic membrane properties and are characteristic regular-spiking neurons. Morphological features examined from biocytin-filled reconstructions as well as retrogradely BDA labeled cells did not reveal any differences. Analysis of spontaneous postsynaptic potentials from callosal neurons did reveal several differences including average amplitude, frequency, and decay time. These findings suggest that callosal neurons in both supra- and infragranular layers have similar phenotypes though belong to different local, intracortical networks.     

Epidemiology and Ecology of Influenza A Viruses among Wildlife in the Arctic

Arctic regions are ecologically significant for the environmental persistence and geographic dissemination of influenza A viruses (IAVs) by avian hosts and other wildlife species. Data describing the epidemiology and ecology of IAVs among wildlife in the arctic are less frequently published compared to southern temperate regions, where prevalence and subtype diversity are more routinely documented. Following PRISMA guidelines, this systematic review addresses this gap by describing the prevalence, spatiotemporal distribution, and ecological characteristics of IAVs detected among wildlife and the environment in this understudied region of the globe. The literature search was performed in PubMed and Google Scholar using a set of pre-defined search terms to identify publications reporting on IAVs in Arctic regions between 1978 and February 2022. A total of 2125 articles were initially screened, 267 were assessed for eligibility, and 71 articles met inclusion criteria. IAVs have been detected in multiple wildlife species in all Arctic regions, including seabirds, shorebirds, waterfowl, seals, sea lions, whales, and terrestrial mammals, and in the environment. Isolates from wild birds comprise the majority of documented viruses derived from wildlife; however, among all animals and environmental matrices, 26 unique low and highly pathogenic subtypes have been characterized in the scientific literature from Arctic regions. Pooled prevalence across studies indicates 4.23% for wild birds, 3.42% among tested environmental matrices, and seroprevalences of 9.29% and 1.69% among marine and terrestrial mammals, respectively. Surveillance data are geographically biased, with most data from the Alaskan Arctic and many fewer reports from the Russian, Canadian, North Atlantic, and Western European Arctic. We highlight multiple important aspects of wildlife host, pathogen, and environmental ecology of IAVs in Arctic regions, including the role of avian migration and breeding cycles for the global spread of IAVs, evidence of inter-species and inter-continental reassortment at high latitudes, and how climate change-driven ecosystem shifts, including changes in the seasonal availability and distribution of dietary resources, have the potential to alter host–pathogen–environment dynamics in Arctic regions. We conclude by identifying gaps in knowledge and propose priorities for future research.     

Allometry in the corpus callosum in neonates: Sexual dimorphism

The corpus callosum (CC) is the largest fiber tract in the human brain, allowing interhemispheric communication by connecting homologous areas of the two cerebral hemispheres. In adults, CC size shows a robust allometric relationship with brain size, with larger brains having larger callosa, but smaller brains having larger callosa relative to brain size. Such an allometric relationship has been shown in both males and females, with no significant difference between the sexes. But there is some evidence that there are alterations in these allometric relationships during development. However, it is currently not known whether there is sexual dimorphism in these allometric relationships from birth, or if it only develops later. We study this in neonate data. Our results indicate that there are already sex differences in these allometric relationships in neonates: male neonates show the adult‐like allometric relationship between CC size and brain size; however female neonates show a significantly more positive allometry between CC size and brain size than either male neonates or female adults. The underlying cause of this sexual dimorphism is unclear; but the existence of this sexual dimorphism in neonates suggests that sex‐differences in lateralization have prenatal origins.     

经额底前纵裂入路显微手术切除巨大型嗅沟脑膜瘤

目的 探讨经额底前纵裂入路显微手术切除巨大型嗅沟脑膜瘤的手术方法及疗效.方法 回顾性分析2018年2月至2020年2月经额底前纵裂入路显微手术切除的10例巨大型嗅沟脑膜瘤的临床资料.结果 按Simpson手术切除标准分级:Simp-son分级Ⅰ级切除1例,Ⅱ级8例,Ⅲ级1例.无手术死亡病例,术后无颅内感染及癫痫等并发症...     

Supratentorial Abnormalities in the Chiari II Malformation,III

Objective. Our clinical observations noted an interhemispheric “cyst,” a protrusion of the posterior superior third ventricle, in fetuses with myelomeningocele (MMC). The study analyzed the frequency of this observation and features that influence its visualization. Methods. We searched for cases of fetal MMC sonographically detected between 1999 and 2007. Intracranial findings were retrospectively reviewed with attention to the interhemispheric cistern. Additionally, we reviewed 25 fetuses without a central nervous system anomaly and 10 fetuses with ventriculomegaly but no MMC. Results. Among 89 fetuses identified, the mean gestational age was 22 weeks 4 days. Thirty‐eight (43%) had an interhemispheric cyst. The frequency was similar on sonograms judged to be well visualized compared with studies judged to be suboptimally visualized. The degree of ventriculomegaly, timing of diagnosis, and severity of the Chiari II malformation did not appear to influence the frequency of the finding. Among fetuses without a central nervous system anomaly, no interhemispheric cysts were detected; a cyst was detected in 1 of 10 fetuses with ventriculomegaly. Interhemispheric cysts were more likely to be detected in fetuses with the Chiari II malformation than fetuses with ventriculomegaly but without the Chiari II malformation (P = .04). Conclusions. Interhemispheric cysts are a common supratentorial feature of the Chiari II malformation. Their presence appears to be unrelated to other features of the Chiari II malformation. Although interhemispheric cysts are seen in other abnormal fetuses, their striking prevalence in the Chiari II malformation should lead to a thorough examination for MMC.     

Changes in cerebral haemodynamics in cases of post-lumbar puncture headache: a prospective transcranial Doppler ultrasound study

We used transcranial Doppler ultrasonography in 45 patients to investigate if changes in haemodynamics in the major arteries of the brain base occurred after lumbar puncture and whether or not patients with or without post-lumbar puncture headache differ with respect to their cerebral haemodynamic parameters before and after lumbar puncture. Before lumbar puncture, patients with post-lumbar puncture headache differed from patients without post-lumbar puncture headache in that they showed significantly higher flow velocities and significant asymmetry of flow velocities with lateralization to the right (p less than or equal to 0.05). Patients without post-lumbar puncture headache, on the other hand, showed non-significant flow velocity lateralization to the left. Forty-eight hours after lumbar puncture, both groups demonstrated symmetrical flow velocities. In addition, only patients with post-lumbar puncture headache showed a significant reduction in the flow velocity of the right middle cerebral artery (p less than or equal to 0.05). These findings suggest that it is not only absolute flow velocity that plays a part in the event of headache, the interhemispheric relation of cerebral haemodynamics also plays a fundamental role.     

Evidence for crossed catecholaminergic nigrostriatal projections by combining wheat germ agglutinin-horseradish peroxidase retrograde transport and tyrosine hydroxylase immunocytochemistry

After unilateral injections of wheat germ agglutinin-horseradish peroxidase into the rat caudate-putamen, a few retrogradely labeled neurons were found in the contralateral pars compacta of the substantia nigra. These contralaterally projecting nigral cell bodies also immunoreacted positively to a specific tyrosine hydroxylase antiserum. We conclude that crossed catecholaminergic nigrostriatal projections may contribute to the reciprocal regulation exerted by the two nigrostriatal dopaminergic systems.     

Interhemispheric Transfer in Normals and Acallosals: Latency Adjusted Evoked Potential Averaging

Interhemispheric transfer time (IHTT) can be estimated from visual evoked potentials (EPs). Latency adjusted averaging (LAA) produces EPs which have enhanced components. LAA also provides estimates of EP latency variance and signal-to-noise ratio (S/N). LAA was tested in analysis of EP-IHTT in normal and acallosal subjects. It was hypothesized that in normals S/N and latency variance would reveal signal degradation resulting from interhemispheric transfer. LAA in normals replicated IHTT findings for both P1 and N1 latency. Latency variance did not increase for cross-callosal measures, whereas the S/N measure showed significant EP degradation due to callosal transfer. EPs from five subjects with callosal absence (two commissurotomy; two complete and one partial callosal agenesis) showed significantly larger than normal latency variability, as well as decreased S/N ratios, for cross-hemisphere visual EPs. Results support the value of LAA in EP research on adequacy of hemispheric interactions in clinical populations.     

Epidermoid tumor of the interhemispheric fissure

In this report, we present a case of an interhemispheric epidermoid presenting with generalized seizure. The tumor was demonstrated radiologically and discussed with the pertinent literature.