Testing retrogenesis and physiological explanations for tract-wise white matter aging: links to developmental order, fibre calibre, and vascularization.

To understand the consistently observed spatial distribution of white-matter (WM) aging, developmentally driven theories termed "retrogenesis" have gained traction, positing that the order of WM tract development predicts the order of declines. Regions that develop first are expected to deteriorate the last, i.e.

Age-Related Alterations in Gray Matter Microstructure in Older People With Remitted Major Depression at Risk for Dementia.

Background: Major depressive disorder (MDD) in late life is a risk factor for mild cognitive impairment (MCI) and Alzheimer's disease. However, studies of gray matter changes have produced varied estimates of which structures are implicated in MDD and dementia. Changes in gray matter volume and cortical thickness are macrostructural measures for the microstructural processes of free water accumulation and dendritic spine loss.

Implications of fitting a two-compartment model in single-shell diffusion MRI.

It is becoming increasingly common for studies to fit single-shell diffusion MRI data to a two-compartment model, which comprises a hindered cellular compartment and a freely diffusing isotropic compartment. These studies consistently find that the fraction of the isotropic compartment () is sensitive to white matter (WM) conditions and pathologies, although the actual biological source of changes inhas not been validated. In this work we put aside the biological interpretation ofand study the sensitivity implications of fitting single-shell data to a two-compartment model.

White matter tract microstructure, macrostructure, and associated cortical gray matter morphology across the lifespan.

Characterizing how, when and where the human brain changes across the lifespan is fundamental to our understanding of developmental processes of childhood and adolescence, degenerative processes of aging, and divergence from normal patterns in disease and disorders. We aimed to provide detailed descriptions of white matter pathways across the lifespan by thoroughly characterizing white matter , white matter , and morphology of the associated with white matter pathways. We analyzed 4 large, high-quality, publicly-available datasets comprising 2789 total imaging sessions, and participants ranging from 0 to 100 years old, using advanced tractography and diffusion modeling.

Feasibility of diffusion-tensor and correlated diffusion imaging for studying white-matter microstructural abnormalities: Application in COVID-19.

There has been growing attention on the effect of COVID-19 on white-matter microstructure, especially among those that self-isolated after being infected. There is also immense scientific interest and potential clinical utility to evaluate the sensitivity of single-shell diffusion magnetic resonance imaging (MRI) methods for detecting such effects. In this work, the performances of three single-shell-compatible diffusion MRI modeling methods are compared for detecting the effect of COVID-19, including diffusion-tensor imaging, diffusion-tensor decomposition of orthogonal moments and correlated diffusion imaging.

Effect of sex on the APOE4-aging interaction in the white matter microstructure of cognitively normal older adults using diffusion-tensor MRI with orthogonal-tensor decomposition (DT-DOME).

The influence of the apolipoprotein E ε4 allele (APOE4) on brain microstructure of cognitively normal older adults remains incompletely understood, in part due to heterogeneity within study populations. In this study, we examined white-matter microstructural integrity in cognitively normal older adults as a function of APOE4 carrier status using conventional diffusion-tensor imaging (DTI) and the novel orthogonal-tensor decomposition (DT-DOME), accounting for the effects of age and sex. Age associations with white-matter microstructure did not significantly depend on APOE4 status, but did differ between sexes, emphasizing the importance of accounting for sex differences in APOE research.

Is adiposity associated with white matter microstructural health and intelligence differently in males and females?

Objective: The role of vascular risk factors in age-related brain degeneration has long been the subject of intense study, but the role of obesity remains understudied. Given known sex differences in fat storage and usage, this study investigates sex differences in the association between adiposity and white matter microstructural integrity, an important early marker of brain degeneration.

Methods: This study assesses the associations between adiposity (abdominal fat ratio and liver proton density fat fraction) and brain health (measures of intelligence and white matter microstructure using diffusion-tensor imaging [DTI]) in a group of UK Biobank participants.

Amyloid-PET of the white matter: Relationship to free water, fiber integrity, and cognition in patients with dementia and small vessel disease.

White matter (WM) injury is frequently observed along with dementia. Positron emission tomography with amyloid-ligands (Aβ-PET) recently gained interest for detecting WM injury. Yet, little is understood about the origin of the altered Aβ-PET signal in WM regions.

DKI enhances the sensitivity and interpretability of age-related DTI patterns in the white matter of UK biobank participants.

Studies of healthy brain aging traditionally report diffusivity patterns associated with white matter degeneration using diffusion tensor imaging (DTI), which assumes that diffusion measured at typical b-values (approximately 1000 s/mm) is Gaussian. Diffusion kurtosis imaging (DKI) is an extension of DTI that measures non-Gaussian diffusion (kurtosis) to better capture microenvironmental processes by incorporating additional data at a higher b-value. In this study, using diffusion data (b-values of 1000 and 2000 s/mm) from 700 UK Biobank participants aged 46-80, we investigate (1) the extent of novel information gained from adding diffusional kurtosis to diffusivity observations in aging, and (2) how conventional DTI metrics in aging compare with diffusivity metrics derived from DKI, which are corrected for kurtosis.

Brain structure and function in people recovering from COVID-19 after hospital discharge or self-isolation: a longitudinal observational study protocol.

Background: The detailed extent of neuroinvasion or deleterious brain changes resulting from COVID-19 and their time courses remain to be determined in relation to "long-haul" COVID-19 symptoms. Our objective is to determine whether there are alterations in functional brain imaging measures among people with COVID-19 after hospital discharge or self-isolation.

Methods: This paper describes a protocol for NeuroCOVID-19, a longitudinal observational study of adults aged 20-75 years at Sunnybrook Health Sciences Centre in Toronto, Ontario, that began in April 2020.

Orthogonal moment diffusion tensor decomposition reveals age-related degeneration patterns in complex fiber architecture.

Diffusion tensor imaging (DTI) consistently detects increased mean diffusivity and decreased fractional anisotropy with advancing age in regions of primarily single white matter (WM) fiber populations, but findings have been inconsistent in regions of more complex fiber architecture. Given that DTI remains more common for characterizing aging WM than advanced diffusion MRI models due to DTI's simplicity, robustness, and efficiency, it is critical to strive to maximize the information extracted from DTI across the entire WM. The present study uses an orthogonal diffusion tensor decomposition based on the 3 eigenvalue moments (mean diffusivity, norm of anisotropy, and mode of anisotropy), yielding clear voxelwise degeneration patterns across the WM, including regions of complex fiber architecture.

Quantitative and correlative extreme ultraviolet coherent imaging of mouse hippocampal neurons at high resolution.

Microscopy with extreme ultraviolet (EUV) light can provide many advantages over optical, hard x-ray or electron-based techniques. However, traditional EUV sources and optics have large disadvantages of scale and cost. Here, we demonstrate the use of a laboratory-scale, coherent EUV source to image biological samples-mouse hippocampal neurons-providing quantitative phase and amplitude transmission information with a lateral resolution of 80 nm and an axial sensitivity of ~1 nm.

The First Ejaculation: A Male Pubertal Milestone Comparable to Menarche?

Boys experience their first ejaculation (thorarche) during adolescence, but this event is often overlooked as a milestone in male adolescent development. The purpose of this article is to draw attention to thorarche and consider it in comparison with the female milestone of menarche. A critical analysis is provided of how thorarche has been interpreted to date and the complexities in construing thorarche from a biological perspective are outlined.

Re-examining age-related differences in white matter microstructure with free-water corrected diffusion tensor imaging.

Diffusion tensor imaging (DTI) has been used extensively to investigate white matter (WM) microstructural changes during healthy adult aging. However, WM fibers are known to shrink throughout the lifespan, leading to larger interstitial spaces with age. This could allow more extracellular free water molecules to bias DTI metrics, which are relied upon to provide WM microstructural information.

Mechano-sensitization of mammalian neuronal networks through expression of the bacterial large-conductance mechanosensitive ion channel.

Development of remote stimulation techniques for neuronal tissues represents a challenging goal. Among the potential methods, mechanical stimuli are the most promising vectors to convey information non-invasively into intact brain tissue. In this context, selective mechano-sensitization of neuronal circuits would pave the way to develop a new cell-type-specific stimulation approach.

Ptychographic coherent diffractive imaging with orthogonal probe relaxation.

Ptychography is a scanning coherent diffractive imaging (CDI) technique that relies upon a high level of stability of the illumination during the course of an experiment. This is particularly an issue for coherent short wavelength sources, where the beam intensity is usually tightly focused on the sample in order to maximize the photon flux density on the illuminated region of the sample and thus a small change in the beam position results in a significant change in illumination of the sample. We present an improved ptychographic method that allows for limited stability of the illumination wavefront and thus significantly improve the reconstruction quality without additional prior knowledge.

Bispyridinium Compounds Inhibit Both Muscle and Neuronal Nicotinic Acetylcholine Receptors in Human Cell Lines.

Standard treatment of poisoning by organophosphorus anticholinesterases uses atropine to reduce the muscarinic effects of acetylcholine accumulation and oximes to reactivate acetylcholinesterase (the effectiveness of which depends on the specific anticholinesterase), but does not directly address the nicotinic effects of poisoning. Bispyridinium molecules which act as noncompetitive antagonists at nicotinic acetylcholine receptors have been identified as promising compounds and one has been shown to improve survival following organophosphorus poisoning in guinea-pigs. Here, we have investigated the structural requirements for antagonism and compared inhibitory potency of these compounds at muscle and neuronal nicotinic receptors and acetylcholinesterase.

Colorectal cancer screening practices in Saskatchewan: Survey of family physicians.

Objective: To evaluate current colorectal cancer (CRC) screening practices in Saskatchewan and identify barriers to screening with the goal of improving current practice.

Design: Survey of family physicians.

Setting: Saskatchewan.

A super-oscillatory lens optical microscope for subwavelength imaging.

The past decade has seen an intensive effort to achieve optical imaging resolution beyond the diffraction limit. Apart from the Pendry-Veselago negative index superlens, implementation of which in optics faces challenges of losses and as yet unattainable fabrication finesse, other super-resolution approaches necessitate the lens either to be in the near proximity of the object or manufactured on it, or work only for a narrow class of samples, such as intensely luminescent or sparse objects. Here we report a new super-resolution microscope for optical imaging that beats the diffraction limit of conventional instruments and the recently demonstrated near-field optical superlens and hyperlens.

An unusual case of fallopian tube intraepithelial carcinoma with mucinous goblet cell differentiation.

► The detection of goblet cell carcinoid in the genital tract is extremely uncommon. ► We report on a patient who presented with a large intraepithelial tubal carcinoma that displayed mucinous, goblet-cell differentiation. ► The optimal management of these lesions may be confounded because their biological behavior is unpredictable.

Protection against nerve agent poisoning by a noncompetitive nicotinic antagonist.

The acute toxicity of organophosphorus (OP) nerve agents arises from accumulation of acetylcholine (ACh) and overstimulation of ACh receptors. The mainstay of current pharmacotherapy is the competitive muscarinic antagonist, atropine. Nicotinic antagonists have not been used due to the difficulties of administering a dose of a competitive neuromuscular blocker sufficient to antagonise the effects of excessive ACh, but not so much that it paralyses the muscles.

In vitro CNS tissue analogues formed by self-organisation of reaggregated post-natal brain tissue.

In this paper, we report the characterization of 'Hi-Spot' cultures formed by the re-aggregation of dissociated postnatal CNS tissue grown at an air-liquid interface. This produces a self-organised, dense, organotypic cellular network. Western blot, immunohistochemical, viral transfection and electron microscopy analyses reveal neuronal and glial populations, and the development of a synaptic network.