Binge drinking in mice:
Researchers from UC Santa Barbara’s Department of Psychological & Brain Sciences recently published a study on the psychological effects of binge drinking in mice. The study aimed to study the interactions between age, sex and the age at which binge drinking began, and their cumulative effects on “negative affect,” or feelings of anxiety and hopelessness, as well as cognitive decline later in life. Previous studies have shown that a history of alcohol abuse is one of the biggest risk factors for Alzheimer’s disease, dementia and other cognitive disorders. In addition, females have been found to be more likely, on average, to drink in order to alleviate feelings of distress, as well as are more likely to exhibit physical and psychological effects from drinking. These experiments, which built upon prior studies of similar design, uniquely segregated males and females temporally in order to reduce potential “chemosensory social stimuli” (i.e. pheromones) and consisted of giving control mice water to drink and binge-drinking mice (of which there were 92) alcohol for two hours a day for 14 days. Then, evaluations for anxiety symptoms were conducted on the mice, including a light-dark shuttle box test, a marble burying test and a swim test. Additionally, evaluations of cognitive impairment were performed, including mazes and spatial recall tests. Both types of experiments were conducted on Day 1 of withdrawal and Day 70. The researchers predicted that the effects of excessive alcohol consumption would be more pronounced in females than males and that a history of binge drinking during adolescence would have more of an effect on behavior than a history of binge drinking during adulthood. A major result of the study found that adolescents drank more alcohol overall than adults, and females drank more than males.
Test-specific results included adult, female binge-drinkers in the box test going into the light less often than their male counterparts, with more time spent in the dark, implying higher anxiety levels. Additionally, adults and females buried more marbles than adolescents and males, also implying higher stress and feelings of hopelessness, and both female and male binge-drinkers spent more time immobile in the swim test than the water drinkers — with immobility being a sign of negative affect. Adult-onset, binge-drinking mice, especially females, were slower to find the hidden platforms and to complete the mazes in the water tests than adolescent-onset binge-drinkers. However, in a subsequent smaller-scale study just looking at Day 1 of withdrawal, the differences in effects between sex and age were less distinct, with relatively few symptoms of negative affect. Overall, there were few effects of “robust binge-drinking” on negative affect and only slight evidence of alcohol-induced cognitive effects. The only significant evidence from the water mazes was that adolescent-onset mice were slightly worse at spatial recall than adult-onset binge drinkers. The authors predict that these results may be related to a lower sensitivity of maze experiments and that two weeks of binge drinking may not be enough to cause significant cognitive effects. Similarly, 3.5 months of age might not be old enough to detect cognitive decline in mice with a history of binge drinking. Nevertheless, despite the need for additional studies on how individual factors like age, sex and age of onset interact, this paper provides promising insight into how a history of drinking in humans could lead to higher chances of developing cognitive disorders later in life.
Gauging glacier cycles:
One of the aspects of climate change that scientists have long been interested in studying is how the planet’s climate has changed over geologic time. With global temperatures on the rise, glacial melting has been an issue of particular concern. It has been concluded that the pattern of glacial cycles over the past 800,000 years or so are approximately 100,000 years (kyr) long, and have to do with changes in Earth’s “Milankovitch cycles.” These three orbital cycles — eccentricity, obliquity and precession — control changes in ice sheet size as the amount of solar radiation reaching different parts of the planet shifts. Until recently, uncertainties regarding the age of ice sheets have made it difficult to determine whether the considerable changes in size were more strongly associated with obliquity — the angle of Earth’s axis of rotation — or precession — the “wobbling” of Earth on its axis as it rotates — although there is significant statistical evidence for both having some impact.
A new study by UCSB’s Department of Earth Science, using improved age estimates, compared the impacts of 41-kyr obliquity cycles and 100-kyr eccentricity cycles on glacial cycles in order to determine which has been historically more responsible for glacial period terminations. Many experts to date believe that cycles of eccentricity — the shape of Earth’s orbit shape — modulate the amplitude of the Earth’s precession, allowing for periods of lower “insolation,” or the amount of solar radiation reaching a particular area — in this case, the ice sheets in question. Additionally, it was hypothesized that precession cycles allow for higher intensity of and changes in insolation, especially during the summer months, which could account for dramatic changes in ice sheet size. The contrasting hypothesis maintains that glacial terminations during the Late Pleistocene Epoch occurred every two to three cycles of obliquity, which therefore must be the primary driver of ice sheet variability. The paper outlines their methodology and how they dated glacial terminations in order to quantify the effect of the various orbital cycles. The team used records of sea level change over geologic time, alongside age estimates derived from correlating “ice-rafted debris” in the North Atlantic Ocean to instances of abrupt Asian monsoon variability. After extensive statistical analysis, the researchers ultimately found that while both precession and obliquity phases have statistically significant effects on glacial termination onset, the precession phase seems to be, by its forcing of summer insolation intensity, more predictive of termination onset, particularly for the largest events.
Many diseases and disorders result from the combination of our past experiences of stress and trauma. Late-onset health conditions, unfortunately, appear many times seemingly out of the blue, and too late to stop before they get out of hand. Our cells, however, hold memories of our past experiences, which can potentially be used to predict and influence the way we react to future physiological stressors. A team of researchers at UCSB, led by senior author and Department of Molecular, Cellular, and Developmental Biology assistant professor Max Wilson recently found a way to map out our histories of cellular stress, known as a “cellular stress memory landscape,” in order to explore how stress-induced diseases occur.
When our bodies encounter stressors like pathogens, toxins or experiences of trauma, something called the integrated stress response (ISR) is initiated. The ISR is a signaling pathway our cells use to adapt to negative conditions. The stress memory landscape is a central part of the ISR mechanism and holds key information regarding our bodies’ ability to protect themselves and regenerate. The researchers in this study developed a way to induce ISR using simulated stress, by shining light on certain light-responsive proteins within the system. This allowed them to observe the direct effects of stress without any permanent damage or cascading effects potentially affecting the body’s response. They also created a model to see whether future stress responses depend on past responses. The results of this study, including that cellular stress memory is a combination of past stress and recovery time, may have significant implications for the future of disease prevention. If ISR pathways can be manipulated in this way, as well as potentially cellular stress memory landscapes, this could one day allow the ability to identify early on, and possibly even prevent, stress-induced diseases and conditions, including those relating to the malfunctioning of stress responses.
A version of this article appeared on p. 16 of the August 24 2023 print edition of the Daily Nexus.