In This Issue

doi:10.1073/iti0117114

Stradivari’s wood may hold clues to violins’ acoustics

1709 Stradivarius violin nicknamed “Marie Hall, Viotti.” Image courtesy of Chimei Museum (Tainan City, Taiwan).

Stradivarius violins have long been prized for superior acoustics, presumed to stem from closely guarded trade secrets and the properties of wood used by 17th-century violin makers from Cremona, Italy. Hwan-Ching Tai et al. (pp. 27–32) tested the premise using an array of analytical techniques to compare modern violin tonewood with maple samples from five Cremonese instruments of distinct provenance. Three centuries of antiquity had decomposed one-third of the hemicellulose, reduced the moisture content, and oxidized lignin in the Stradivarius samples, compared with modern tonewood. In contrast, cellulose in the aged samples largely remained impervious to time, retaining its crystalline structure and mechanical strength. Maples from the master craftsman’s violins, but not his cellos, displayed heat-oxidation patterns atypical for natural wood but previously reported in wood subjected to fungal rot; the authors suggest that the patterns may be the result of high-frequency vibrations. Chemical analysis of inorganic elements suggested that the antique maples may have been treated with mineral preservatives, partly explaining their distinct elemental composition and the seeming resistance to worm damage reported in Cremonese violins. Modern samples showed no signs of mineral infusion, a practice thought to be uncommon among violin makers outside Cremona. According to the authors, further analysis might reveal whether aging, chemical treatment, and physical vibrations can together account for the vaunted tonality of Stradivarius violins. — P.N.

Ultrasound disruption of blood–brain barrier

The fibrous appearance in this TUNEL stain after pFUS+MB treatment is consistent with inflammation in the brain parenchyma.

Noninvasive neurodegenerative disease treatments that open the blood–brain barrier (BBB), which prevents the passage of molecules that could induce cellular damage and inflammation in the brain, have been put forth as possible methods for therapeutic drug or gene delivery. Zsofia Kovacs et al. (pp. E75–E84) used MRI to determine how the brains of rats were affected by pulsed focused ultrasound (pFUS) combined with systemic ultrasound contrast agent microbubble (MB) treatment. Following pFUS+MB–induced BBB disruption, the authors found a number of proteomic and transcriptomic changes in the rat brains, including a release of damage-associated molecular patterns that led to a sterile inflammation response in the brain parenchyma. Further histological analysis revealed that following pFUS+MB–induced BBB disruption, levels of certain molecular and cellular markers of inflammation in the brain parenchyma and vasculature were elevated for up to 24 hours, and that the abundance of macrophages increased, consistent with an innate immune response. The results suggest that pFUS+MB techniques might induce a sterile inflammatory response comparable to that of decreased blood supply or mild brain injury events. Further study might be required before pFUS+MB can be used in clinical settings, according to the authors. — C.S.

Climate and dengue dynamics

Mosquito control efforts to prevent dengue. (Inset) Dengue vector Aedes albopictus.

Dengue is a mosquito-borne disease that is rapidly spreading worldwide, having increased in incidence 30-fold over the past 50 years. Dengue outbreaks are influenced by both climate and socioeconomic factors, but the quantitative relationship of these factors to dengue incidence is poorly understood. To quantitatively model the effects of climate on dengue, Lei Xu et al. (pp. 113–118) analyzed data on the monthly incidence of dengue, adult mosquito density, temperature, and rainfall over the period 2005–2015 in the city of Guangzhou in southern China. High monthly average maximum temperatures were associated with increased likelihood of dengue outbreaks, whereas both high temperature and a high number of days with rainfall were associated with increased outbreak severity. The authors also found an association between the number of days with rainfall and adult mosquito density, suggesting an indirect effect of rainfall on dengue incidence. A model of adult dengue incidence based on data from 2005 to 2012 accurately predicted the observed dengue incidence over the next 3 years. According to the authors, the results demonstrate how climate influences vector-borne diseases and may aid dengue control and prevention. — B.D.

El Niño and Zika virus spread

Asian tiger mosquito. Image courtesy of the CDC.

Climate can influence the transmission risk of mosquito-borne viruses, but few studies have modeled how climate might affect the spread of Zika virus (ZIKV) by both of its two major vectors: the yellow fever mosquito (Aedes aegypti), found in tropical regions, and the Asian tiger mosquito (Aedes albopictus), found in tropical and temperate climes. Cyril Caminade et al. (pp. 119–124) used estimates of the worldwide distribution of both vectors as well as temperature-dependent factors, such as mosquito biting and mortality rates and viral maturation periods within mosquitoes, to predict the effect of climate on ZIKV transmission. The authors’ model suggests that in 2015, ZIKV transmission risk, as measured by the average number of secondary infections triggered by a primary infection in a susceptible population, was greatest in South America, partly driven by temperatures conducive to high biting rates and low mosquito mortality rates and viral incubation periods; ZIKV is suspected to have entered the continent in 2013. The 2015 El Niño, together with climate warming, likely abetted the ZIKV outbreak in Latin America. Further, the model predicts a potential seasonal transmission risk, driven by A. albopictus, in the southeastern United States, southern China, and southern Europe, during summer in the Northern hemisphere. The findings could help public health officials tailor mosquito control measures and travel advisories, according to the authors. — P.N.