Cortical diurnal rhythms remain intact with microglial depletion

Microglia are subject to change in tandem with the endogenously generated biological oscillations known as our circadian rhythm. Studies have shown microglia harbor an intrinsic molecular clock which regulates diurnal changes in morphology and influences inflammatory responses. In the adult brain, microglia play an important role in the regulation of condensed extracellular matrix structures called perineuronal nets (PNNs), and it has been suggested that PNNs are also regulated in a circadian and diurnal manner. We sought to determine whether microglia mediate the diurnal regulation of PNNs via CSF1R inhibitor dependent microglial depletion in C57BL/6J mice, and how the absence of microglia might affect cortical diurnal gene expression rhythms. While we observe diurnal differences in microglial morphology, where microglia are most ramified at the onset of the dark phase, we do not find diurnal differences in PNN intensity. However, PNN intensity increases across many brain regions in the absence of microglia, supporting a role for microglia in the regulation of PNNs. Here, we also show that cortical diurnal gene expression rhythms are intact, with no cycling gene changes without microglia. These findings demonstrate a role for microglia in the maintenance of PNNs, but not in the maintenance of diurnal rhythms.

White Fang Ally: The Arctic As Eden of Death in 30 Days of Night

A recurrent congenital weakness of 20th and 21st century television, literature, and cinema vampires is their porphyric susceptibility to ultraviolet radiation. Central to vampires’ continued undead life is the problem of sunlight. In this way, sunless environs like the Arctic and Antarctic represent what I describe as purely Gothic environments in whose desolation, cold, and darkness, undead life is able to proliferate, unmarred and unimpeded by the typical diurnal/nocturnal cycles of luminosity that trouble the undead lives of vampires. In order to theorize the value of the Arctic as an embodiment of Gothic-horror, this essay uses Steve Niles and Ben Templesmith’s 30 Days of Night (2002) as a case study of the pathetic resonances between the Arctic and the figure of the vampire. Following on from this, the analysis turns to Michel Foucault’s concept of the heterotopia in order to theorize the manner in which the Arctic, whose nocturnal/diurnal rhythms stand in radical opposition to the majority of seasonal cycles elsewhere on earth, represents an onto-existential paradise of death for the undead: a chronotope that embodies the essential attributes of the onto-existential condition of the undead.

Methionine Restriction Improves Gut Barrier Function by Reshaping Diurnal Rhythms of Inflammation-Related Microbes in Aged Mice

Age-related gut barrier dysfunction and dysbiosis of the gut microbiome play crucial roles in human aging. Dietary methionine restriction (MR) has been reported to extend lifespan and reduce the inflammatory response; however, its protective effects on age-related gut barrier dysfunction remain unclear. Accordingly, we focus on the effects of MR on inflammation and gut function. We found a 3-month methionine-restriction reduced inflammatory factors in the serum of aged mice. Moreover, MR reduced gut permeability in aged mice and increased the levels of the tight junction proteins mRNAs, including those of occludin, claudin-1, and zona occludens-1. MR significantly reduced bacterial endotoxin lipopolysaccharide concentration in aged mice serum. By using 16s rRNA sequencing to analyze microbiome diurnal rhythmicity during 24 h, we found MR moderately recovered the cyclical fluctuations of the gut microbiome which was disrupted in aged mice, leading to time-specific enhancement of the abundance of short-chain fatty acid-producing and lifespan-promoting microbes. Moreover, MR dampened the oscillation of inflammation-related TM7-3 and Staphylococcaceae. In conclusion, the effects of MR on the gut barrier were likely related to alleviation of the oscillations of inflammation-related microbes. MR can enable nutritional intervention against age-related gut barrier dysfunction.

Phenome-Wide Association Study of Actigraphy in the UK Biobank

Wrist-worn accelerometer actigraphy devices present the opportunity for large-scale data collection from people during their daily lives. Using data from approximately 100,000 participants in the UK Biobank, actigraphy-derived measures of physical activity, sleep, and diurnal rhythms were associated in exploration and validation cohorts with a full phenome-wide set of diagnoses, biomarkers and metadata. Rhythmicity was captured by two independent models based on accelerometer and skin temperature harnessing behavioral (diurnal) and molecular (circadian) components. We found that robust rhythms significantly with biomarkers, survival, and phenotypes including diabetes, hypertension, mood disorders, and chronic airway obstruction; these associations were comparable to those with physical activity and sleep. Surprisingly, associations were mostly consistent between the sexes, while modulation by age was significant. More importantly, rhythms were found to be powerful predictors of future diseases: a two standard deviation difference in wrist temperature rhythms corresponded to increases in rate of diagnosis of 61% in diabetes, 38% in chronic airway obstruction, 27% in anxiety disorders, and 22% in hypertension. Our PheWAS of actigraphy data in the UK Biobank establishes that rhythmicity is fundamental to modeling disease trajectories, as are physical activity and sleep. Integration of long-term remote biosensing into patient care could thus afford an individualized approach to risk management.

A haplotype-resolved genome assembly of the Nile rat facilitates exploration of the genetic basis of diabetes

The Nile rat (Avicanthis niloticus) is an important animal model for biomedical research, including the study of diurnal rhythms and type 2 diabetes. Here, we report a 2.5 Gb, chromosome-level reference genome assembly with fully resolved parental haplotypes, generated with the Vertebrate Genomes Project (VGP). The assembly is highly contiguous, with contig N50 of 11.1 Mb, scaffold N50 of 83 Mb, and 95.2% of the sequence assigned to chromosomes. We used a novel workflow to identify 3,613 segmental duplications and quantify duplicated genes. Comparative analyses revealed unique genomic features of the Nile rat, including those that affect genes associated with type 2 diabetes and metabolic dysfunctions. These include 14 genes that are heterozygous in the Nile rat or highly diverged from the house mouse. Our findings reflect the exceptional level of genomic detail present in this assembly, which will greatly expand the potential of the Nile rat as a model organism for genetic studies.

Principles of Neuroendocrinology and Hypothalamic Function

The hypothalamus is the neural center of the endocrine system, the regulator of the autonomic nervous system, and the circadian and seasonal clock for behavioral and sleep-wake functions. The hypothalamus maintains homeostasis by integrating cortical, limbic, and spinal inputs and by affecting hormone release, temperature regulation, intake of food and water, sexual behavior and reproduction, emotional responses, and diurnal rhythms. As the link from the nervous system to the endocrine system, the hypothalamus synthesizes and secretes neurohormones that stimulate or inhibit the secretion of pituitary hormones.

Impact of climate changes on the diurnal behaviour of some passerines in some selected habitats of central Punjab, Pakistan

Present paper provides information on the impact of climate changes on diurnal rhythms of the four passerines viz, house sparrow (Passer domesticus Linn.), rosy starling (Pastor roseus Linn.), tree swallows (Tachycineta bicolor Hirun.), and brown shrike (Lanius cristatus Linn.) for two years period in the four major agricultural habitats viz. Faisalabad, Sheikhupura, Toba Tek Singh and Khanewal of Central Punjab, Pakistan. Effects of climate catastrophe have been seriously recognized as important inhibitory factors for birds’ sustainable existence and conservation. Among the four habitats, present within 120 kilometre radius from Faisalabad district, observations were conducted weekly on active and passive foraging, and the roost exits and returns throughout the day. Weather changes viz. temperature, precipitation and relative humidity were critically recorded. Impacts of temperature were significant and resulted in decline of the active foraging for the four designated birds (β= -2.36, -1.93,-2.15 and -1.64) whereas, precipitation due to its lowered frequency, exerted negative influence on the house sparrow and brown shrike, but was non-significant for rosy starling and tree swallows. Overall, temperature and relative humidity (RH) were the foremost climate factors and largely reduced the foraging and roosting movements of the four passerine birds’. Nonetheless, effects of lowered rainfall for the four habitats throughout this study were non-significant.

Beat perception in polyrhythms: Time is structured in binary units

In everyday life, we group and subdivide time to understand the sensory environment surrounding us. Organizing time in units, such as diurnal rhythms, phrases, and beat patterns, is fundamental to behavior, speech, and music. When listening to music, our perceptual system extracts and nests rhythmic regularities to create a hierarchical metrical structure that enables us to predict the timing of the next events. Foot tapping and head bobbing to musical rhythms are observable evidence of this process. In the special case of polyrhythms, at least two metrical structures compete to become the reference for these temporal regularities, rendering several possible beats with which we can synchronize our movements. While there is general agreement that tempo, pitch, and loudness influence beat perception in polyrhythms, we focused on the yet neglected influence of beat subdivisions, i.e., the least common denominator of a polyrhythm ratio. In three online experiments, 300 participants listened to a range of polyrhythms and tapped their index fingers in time with the perceived beat. The polyrhythms consisted of two simultaneously presented isochronous pulse trains with different ratios (2:3, 2:5, 3:4, 3:5, 4:5, 5:6) and different tempi. For ratios 2:3 and 3:4, we additionally manipulated the pitch of the pulse trains. Results showed a highly robust influence of subdivision grouping on beat perception. This was manifested as a propensity towards beats that are subdivided into two or four equally spaced units, as opposed to beats with three or more complex groupings of subdivisions. Additionally, lower pitched pulse trains were more often perceived as the beat. Our findings suggest that subdivisions, not beats, are the basic unit of beat perception, and that the principle underlying the binary grouping of subdivisions reflects a propensity towards simplicity. This preference for simple grouping is widely applicable to human perception and cognition of time.