Conserving biodiverse habitats
Contextual habitat intactness for biodiversity. Dark shades indicate high intactness, and colors indicate levels of human influence (Blue = wilderness, Green = low disturbance, Orange = modified, Pink = highly modified).
Natural habitat loss contributes to biodiversity loss, and by some estimates nearly half a million species are in danger of extinction over the coming decades. However, it is unclear whether protecting large and intact natural systems, such as wilderness, is as important as protecting small areas of highly threatened habitats within degraded environments. To identify high-value biodiversity habitats, Karel Mokany et al. (pp. 9906–9911) combined global data on habitat conditions with models of species assemblage turnover that included data for more than 400,000 species. The analysis revealed that large, intact habitats are important to protect, but fragmented and degraded habitats can prove essential to conserving biodiversity because they may support species that have lost much of their habitat elsewhere through anthropogenic modification. The authors also found that 18.6% of high-value biodiversity habitats are located within protected areas. Furthermore, only 6% of high-value biodiversity habitats in regions subjected to high levels of human modification are protected. The largest areas of unprotected high-value biodiversity habitat are within wilderness and locations that experience low disturbance from humans. Both intact and threatened habitats may be important to protect, given the importance of regional and environmental factors to biodiversity conservation, according to the authors. — M.S.
Population age structure and COVID-19 mortality
The progression and impact of coronavirus disease 2019 (COVID-19) may depend on the age structure of the population, given that mortality risk is concentrated among the elderly. Jennifer Beam Dowd et al. (pp. 9696–9698) calculated the expected number of deaths for various countries based on the age distribution within the population and assuming an infection prevalence of 10% and the age-specific mortality of Italy as of March 30, 2020. Around 23% of Italy’s population is over age 65, making it one of the oldest populations in the world, and Italy has experienced a correspondingly high overall case fatality rate of 10.6%. In this scenario, the authors projected more than 300,000 expected fatalities for Italy. In South Korea, where only 4.5% of cases have occurred in people aged 80 years or older, expected fatalities were fewer than 180,000. The authors also considered Brazil and Nigeria, which have similar populations but different age distributions. Brazil, with 2% of the population aged 80 years or older, was expected to have more than three times the number of fatalities as Nigeria, where only 0.2% of the population is aged 80 years or older. According to the authors, the results suggest that disease mitigation policies, such as social distancing, should consider both the age distribution within the population as well as intergenerational social contacts. — B.D.
Cannabinoid exposure and cocaine response
Cannabis plant, White Widow strain. Image credit: Flickr/Théo.
The endocannabinoid system modulates reward and cognitive processes in the brain and plays a central role in neurodevelopment. Cannabis use among adolescents has been associated with increased risk of subsequent cocaine use and thought to alter the brain’s response to cocaine and other addictive substances. Maria Scherma et al. (pp. 9991–10002) examined epigenetic responses, gene expression, and other biochemical changes in the brains of rats that resulted from cocaine exposure, with and without prior exposure to a synthetic cannabinoid. Prior exposure to cannabinoids resulted in an enhanced response to cocaine’s stimulatory effects in adolescent rats, but not adult rats. The enhanced behavioral response was associated with increased histone acetylation and reduced levels of the enzyme histone deacetylase 6 in the brain’s prefrontal cortex. Cannabinoid exposure also led to alterations in cocaine-induced gene expression patterns, alternative splicing events in genes related to neurotransmitter receptor membrane localization, and enhanced effects of cocaine on protein phosphorylation. The results suggest that cannabinoid exposure during adolescence alters the initial behavioral, molecular, and epigenetic responses to cocaine, potentially enhancing susceptibility to addiction in vulnerable individuals, according to the authors. — B.D.
Effects of fetal alcohol exposure
Early intervention for infants experiencing fetal alcohol syndrome can reduce long-term cognitive and behavioral impacts. Recent advances in motion correction have improved the quality and resolution of 3D MRI of the fetal brain. Using in utero MRI, Xiaojie Wang et al. (pp. 10035–10044) found that exposure to alcohol in the first trimester affects the development of brain regions involved in motor control in rhesus macaques. The authors examined a group of 28 female macaques. Fourteen of the macaques consumed 1.5 g of alcohol per kilogram of body weight per day. At three time points during gestation, the authors used in utero MRI to image the fetal brains, immediately followed by electrophysiological assays of brain activity. Total brain volumes of ethanol-exposed and control fetuses did not differ. In the human equivalent of the third trimester, however, both the cerebellum and brain stem regions in the ethanol-exposed fetuses were smaller, and motor-related white matter maturation was altered, compared with controls. Electrophysiological recordings suggested that the differences are functionally significant. According to the authors, noninvasive in utero MRI may be sufficiently sensitive to be developed as a diagnostic tool for fetal alcohol syndrome as early as the third trimester. — T.H.D.
Potential biomarker of geographic atrophy
Studies have identified many risk loci that can contribute to the initiation and progression of age-related macular degeneration (AMD), including the trimeric serine hydrolase high-temperature requirement 1 (HtrA1). Irene Tom, Victoria Pham, et al. (pp. 9952–9963) designed an anti-HtrA1 Fab inhibitor of HtrA1 proteolytic activity to investigate the function of HtrA1 in the eye and its role in AMD pathology. The authors generated an HtrA1-directed activity-based small molecule probe to track target engagement in vivo and used an N-terminomic proteomic profiling approach in preclinical models to identify HtrA1-specific substrates. The authors identified three eye-specific substrates that can potentially serve as biomarkers of anti-HtrA1 Fab activity in the human eye: Retinol Binding Protein 3, Clusterin, and Dickkopf-related protein 3 (DKK3). Of these substrates, DKK3 was found to be a robust pharmacodynamic biomarker for anti-HtrA1 Fab activity in animal models. In addition, the authors showed in a Phase 1 study that HtrA1-mediated cleavage of DKK3 in patients with geographic atrophy provided evidence of anti-HtrA1 Fab activity and information on activity duration. According to the authors, DKK3 could serve as an eye-specific pharmacodynamic biomarker for monitoring ocular protease activity in AMD. — S.R.
Milk consumption by ancient herders
Ceremonial ceramics from the Jarigole Pillar Site in northwestern Kenya were analyzed for lipid residues. Image credit: Elizabeth Sawchuk (University of Alberta, Edmonton, Canada).
Lactase persistence (LP), the ability to digest milk into adulthood, facilitates the milk-based, high-protein, low-calorie diet that eastern African herding communities have historically relied on. Multiple genetic bases for LP in contemporary eastern African populations are known, but the food consumption patterns of early eastern African herders and the context in which LP evolved remain poorly understood. Katherine Grillo, Julie Dunne, et al. (pp. 9793–9799) analyzed lipid residues from 125 ceramic vessels from four archaeological sites in Kenya and Tanzania dated to the Pastoral Neolithic, approximately 5,000–1,200 years ago. The carbon isotope compositions of fatty acids from these residues indicated the presence of milk from ruminant animals in some of the samples, whereas other samples were consistent with adipose tissue or mixtures of milk and adipose tissue. The majority of samples from the two later sites came from ruminant adipose tissue, but samples from milk were present as well. Samples from one of the later sites also contained lipid distributions that likely originated from plants, suggesting that the vessels containing the residues were used for plant processing. The results provide the earliest direct evidence for milk, meat, and plant consumption by eastern African pastoralist societies and shed light on the distinctive evolution of LP in the region, according to the authors. — B.D.