Circadian Rhythms in the Neuronal Network Timing the Luteinizing Hormone Surge

For 3.5 billion years before electric light was invented in 1879, life on Earth evolved under the pattern of light during the day and darkness during the night. Through evolution, nearly all organisms internalized the temporal rhythm of Earth’s 24-hour rotation and evolved self-sustaining biological clocks with a ~24-hour rhythm. These internal rhythms are called circadian rhythms, and the molecular constituents that generate them are called molecular circadian clocks. Alignment of molecular clocks with the environmental light-dark rhythms optimizes physiology and behavior. This is particularly true for reproductive function, in which seasonal breeders use day-length information to time yearly changes in fertility. However, it is becoming increasingly clear that light-induced disruption of circadian rhythms can negatively impact fertility in non-seasonal breeders as well. In particular, the luteinizing hormone surge promoting ovulation, is sensitive to circadian disruption. In this review, we will summarize our current understanding of the neuronal networks that underlie circadian rhythms and the luteinizing hormone surge.

Stroke risk based on classification of atrial fibrillation: real-world vs clinical trial

Background The most widely accepted clinical classification of atrial fibrillation (AF) is according to temporal rhythm-based patterns, reflecting the notion that most patients initially suffer from transient episodes that prolong over time due to atrial substrate remodelling as the disease progresses. Therefore, it may be speculated that patients with extended episodes of “continuous” AF (persistent, long-standing persistent and permanent AF) may be at higher risk of stroke complications compared to paroxysmal AF (pAF). However, the risk of stroke according to clinical classification of AF remains poorly defined. In this study, we assessed the impact of AF type on stroke risk in patients with AF from “real-world” and “clinical trial” cohorts. Methods Post-hoc analysis of patient-level data from the Murcia AF Project and AMADEUS trial. All patients were anticoagulated. Patients were grouped into those with pAF and non-pAF. pAF was defined as AF that terminates spontaneously or with intervention within seven days of onset. Non-pAF was defined as AF that lasted longer than seven days, including persistent, long-standing persistent and permanent AF subtypes. Study endpoint was the incidence rate of ischaemic stroke. A modified CHA2DS2-VAS“c” score that applied one additional point for a “c” criterion of continuous AF (i.e. non-pAF) was calculated. Results 5,917 patients were included; 1,361 (23.0%) real-world and 4,556 (77.0%) clinical trial. Real-world patients had a median age of 76 (interquartile range [IQR] 71–81) years with 51.3% females compared to a median age of 71 (IQR 64–77) years with 33.5% females among clinical trial participants. Baseline demographics were comparable in both groups in the real-world cohort but clinical trial participants with non-pAF were older, predominantly male and had more comorbidities compared to those with pAF. Crude stroke rates were comparable between the groups in real-world patients (incidence rate ratio [IRR] 0.72 [95% CI, 0.37–1.28], p=0.259) though clinical trial participants with non-pAF (vs. pAF) had a significantly higher crude rate of stroke events (IRR 4.66 [95% CI, 2.41–9.48], p<0.001). Using multivariable cox regression analysis, AF type was not independently associated with stroke risk in the real-world (adjusted hazard ratio [HR] 1.41 [95% CI, 0.80–2.50], p=0.239) and clinical trial (adjusted HR 1.17 [95% CI, 0.62–2.20], p=0.621) cohorts, after accounting for known risk factors using the CHA2DS2-VASc score. Using receiver operating characteristic curves analysis, we found no significant improvement in the CHA2DS2-VAS“c” compared to CHA2DS2-VASc score in either cohort (p>0.05). Conclusion Overall, there was no association between the temporal rhythm-based patterns of AF and stroke risk among anticoagulated patients, suggesting that this should not be a consideration when assessing the need for anticoagulation in AF. FUNDunding Acknowledgement Type of funding sources: None.

Temporal Rhythm Affects the Efficiency of Asian Citrus Psyllid (Diaphorina citri) to Acquire Huanglongbing Pathogen

Huanglongbing, commonly known as citrus greening, is a devastating disease of citrus worldwide. Candidatus liberibacter asiaticus is the putative cause of citrus greening disease in China and is spread through the process of plant grafting and feeding by insect vectors. Asian citrus psyllid (Diaphorina citri) is a destructive pest due to insecticide resistance development and the main cause of dissemination of Huanglongbing. The purpose of this study was to determine the level of Huanglongbing present in Guangdong province and the acquisition of the pathogen by D. citri through feeding. Six different city areas of Guangdong province were sampled. The results demonstrated that Yunfu currently has the highest infestation rate of CLas in Guangdong province, followed by Chaozhou, Jiangmen, and Foshan. In comparison, Zhongshan and Maoming have the lowest infestation rates. Results also showed that CLas acquisition was directly proportional to the insect feeding duration. The longer an insect fed on an infested plant, the more CLas it acquired. The acquisition efficiency of the pathogen was higher at night compared to during the daytime. During the time period of 15:00–07:00 D. citri acquires more pathogens than during the period of 07:00–15:00. This study provides a basic understanding of the feeding pattern of D. citri, which aids in devising a management program for effective control of direct and indirect losses caused by D. citri.

The Low-Density Urban Systems of the Classic Period Maya and Izapa: Insights from Settlement Scaling Theory

The peoples of southern Mesoamerica, including the Classic period Maya, are often claimed to exhibit a distinct type of spatial organization relative to contemporary urban systems. Here, we use the settlement scaling framework and properties of settlements recorded in systematic, full-coverage surveys to examine ways in which southern Mesoamerican settlement systems were both similar to and different from contemporary systems. We find that the population-area relationship in these settlements differs greatly from that reported for other agrarian settlement systems, but that more typical patterns emerge when one considers a site epicenter as the relevant social interaction area, and the population administered from a given center as the relevant interacting population. Our results imply that southern Mesoamerican populations mixed socially at a slower temporal rhythm than is typical of contemporary systems. Residential locations reflected the need to balance energetic and transport costs of farming with lower-frequency costs of commuting to central places. Nevertheless, increasing returns in activities such as civic construction were still realized through lower-frequency social mixing. These findings suggest that the primary difference between low-density urbanism and contemporary urban systems lies in the spatial and temporal rhythms of social mixing.

Discrimination of regular and irregular rhythms by accumulation of time differences

Perceiving the temporal regularity in a sequence of repetitive sensory events facilitates the preparation and execution of relevant behaviors with tight temporal constraints. How we estimate temporal regularity from repeating patterns of sensory stimuli is not completely understood. We developed a decision-making task in which participants had to decide whether a train of visual, auditory, or tactile pulses, had a regular or an irregular temporal pattern. We tested the hypothesis that subjects categorize stimuli as irregular by accumulating the time differences between the predicted and observed times of sensory pulses defining a temporal rhythm. Results show that instead of waiting for a single large temporal deviation, participants accumulate timing-error signals and judge a pattern as irregular when the amount of evidence reaches a decision threshold. Model fits of bounded integration showed that this accumulation occurs with negligible leak of evidence. Consistent with previous findings, we show that participants perform better when evaluating the regularity of auditory pulses, as compared with visual or tactile stimuli. Our results suggest that temporal regularity is estimated by comparing expected and measured pulse onset times, and that each prediction error is accumulated towards a threshold to generate a behavioral choice.

Unsettling the ‘New’? Apartheid Did Not Die (Lowery, 1998)

The documentary film Apartheid Did Not Die (Lowery, 1998) raises a theoretical problematic concerning the nature of historical change. In this article, an attempt is made to understand how the film represents the ‘post’ in the post-apartheid era, particularly with regard to its premises about historical change in societies that have recently emerged from an oppressive past, and the responses that the film occasioned. I show that through narrative and documentary strategies, Apartheid Did Not Die institutes a singular temporal rhythm for South Africa and is as such a metanarrative. Yet, it is as a metanarrative that the film occasioned a wide array of public engagements. Though powerful and provocative, the film’s arguments point to the limits of generalizing analyses and polemical modes of representation. However, its generalizing tone also shows the productivity of polemic as occasioned by the public responses it brought into being. Considering the theoretically problematic elements of the documentary form offers a critical perspective on the responses the film elicited in the public sphere.

The Genetics of Mating Song Evolution Underlying Rapid Speciation: Linking Quantitative Variation to Candidate Genes for Behavioral Isolation

Differences in mating behaviors evolve early during speciation, eventually contributing to reproductive barriers between species. Knowledge of the genetic and genomic basis of these behaviors is therefore integral to a causal understanding of speciation. Acoustic behaviors are often part of the mating ritual in animal species. The temporal rhythms of mating songs are notably species-specific in many vertebrates and arthropods and often underlie assortative mating. Despite discoveries of mutations that disrupt the temporal rhythm of these songs, we know surprisingly little about genes affecting naturally occurring variation in the temporal pattern of singing behavior. In the rapidly speciating Hawaiian cricket genus Laupala, the striking species variation in song rhythms constitutes a behavioral barrier to reproduction between species. Here, we mapped the largest-effect locus underlying interspecific variation in song rhythm between two Laupala species to a narrow genomic region, wherein we find no known candidate genes affecting song temporal rhythm in Drosophila. Whole-genome sequencing, gene prediction, and functional annotation of this region reveal an exciting and promising candidate gene, the putative cyclic nucleotide-gated ion channel-like gene, for natural variation in mating behavior, suggesting that ion channels are important targets of selection on rhythmic signaling during establishment of behavioral isolation and rapid speciation.

The Temporal Rhythm of Alcohol Consumption: On the Development of Young People’s Weekly Drinking Patterns

This article investigates young people’s weekly drinking patterns during late adolescence and young adulthood. The article builds a disaggregated and temporal framework to explain how young people drink on certain days. Using sequence analysis techniques on longitudinal data from a representative Danish survey, the article identifies four drinking patterns (the majority, the weekend drinkers, the weekend bingers and the heavy drinkers). Analyses of the transitions between the drinking patterns reveal non-linear developments where heavy drinking at an early age does not necessarily lead to heavy drinking later in life. Although parental income and education are important factors to explain whether young people begin to drink at an early age, high levels of alcohol consumption during youth is more associated with influenced from peers and partners.