《自然》（20190711出版）一周論文導讀

翻譯 | 宗華

Nature, 11 July 2019, Volume 571 Issue7764

《自然》2019年7月11日，第571卷7764期

生物學Biology

Neural signatures of sleep in zebrafish

斑馬魚睡眠的神經特徵

作者：Louis C. Leung, Gordon X. Wang, Romain Madelaine, et al

鏈接：

https://www.nature.com/articles/s41586-019-1336-7

摘要：

慢波睡眠和快速眼動睡眠在哺乳動物、鳥類和蜥蜴中都有發現，但目前尚不清楚這些神經元特徵是否也出現在非羊膜脊椎動物中。

這裡，我們開發了一種無創的基於熒光的斑馬魚多導睡眠圖，並利用無偏見的、全腦範圍的活動記錄，結合對眼球運動、肌肉動力學和心率的評估，證明斑馬魚至少有兩種主要的睡眠特徵。

這些特徵被我們稱為慢脈衝睡眠和傳播波睡眠，與慢波睡眠和快速眼動睡眠有共同之處。此外，我們發現，聚集黑色素的激素信號（涉及哺乳動物的睡眠）也調控著斑馬魚的傳播波睡眠信號和總睡眠量，而這可能是通過激活室管膜細胞實現的。

這些觀察結果表明，4.5億年前，脊椎動物大腦中可能已經出現了睡眠的共同神經信號。

Abstract

Slow-wave sleep and rapid eye movement (or paradoxical) sleep have been found in mammals, birds and lizards, but it is unclear whether these neuronal signatures are found in non-amniotic vertebrates. Here we develop non-invasive fluorescence-based polysomnography for zebrafish, and show—using unbiased, brain-wide activity recording coupled with assessment of eye movement, muscle dynamics and heart rate — that there are at least two major sleep signatures in zebrafish. These signatures, which weterm slow bursting sleep and propagating wave sleep, share commonalities with those of slow-wave sleep and paradoxical or rapid eye movement sleep, respectively. Further, we find that melanin-concentrating hormone signalling (which is involved in mammalian sleep) also regulates propagating wave sleep signatures and the overall amount of sleep in zebrafish, probably via activation of ependymal cells. These observations suggest that common neural signatures of sleep may have emerged in the vertebrate brain over 450 million years ago.

Single-cell analysis reveals T cell infiltration in old neurogenic niches

單細胞分析顯示老年神經源性小生境中的T細胞浸潤

作者：Ben W. Dulken, Matthew T. Buckley, Paloma Navarro Negredo, et al

鏈接：

https://www.nature.com/articles/s41586-019-1362-5

摘要：

哺乳動物的大腦包含神經源性小生境，而後者又包括神經幹細胞和其他類型的細胞。隨著年齡的增長，神經源性小生境的功能減弱，但它們在衰老過程中如何變化仍不清楚。

這裡，我們對小鼠的年輕和年老神經源性小生境進行了單細胞RNA測序。對14685個單細胞轉錄組的分析顯示，活化的神經幹細胞數量減少，內皮細胞和小膠質細胞發生變化，同時老年神經源性小生境中T細胞浸潤。

老年大腦中的T細胞是無性擴增的，並且通常與老年血液中的T細胞不同。這表明它們可能經歷了特定的抗原。老年大腦中的T細胞在表達γ干擾素，同時具有很高干擾素反應的神經幹細胞子集顯示出減少的體內增殖。

我們的研究揭示了老年大腦中T細胞和神經幹細胞之間的相互作用，為抵消與年齡有關的大腦功能衰退開闢了潛在的途徑。

Abstract

The mammalian brain contains neurogenic niches that comprise neural stem cells and other cell types. Neurogenic niches become less functional with age, but how they change during ageing remains unclear. Here we perform single-cell RNA sequencing of young and old neurogenic niches in mice. The analysis of 14,685 single-cell transcriptomes reveals a decrease in activated neural stem cells, changes in endothelial cells and microglia, and an infiltration of T cells in old neurogenic niches. T cells in old brains are clonally expanded and are generally distinct from those in old blood, which suggests that they may experience specific antigens. T cells inold brains also express interferon-γ, and the subset of neural stem cells that has a high interferon response shows decreased proliferation in vivo. Our study reveals an interaction between T cells and neural stem cells in old brains, opening potential avenues through which to counteract age-related decline in brain function.

Foot callus thickness does not trade off protection for tactile sensitivity during walking

足部老繭厚度不會抵消走路時對觸覺敏感性的保護

作者：Nicholas B. Holowka, Bert Wynands, Tina J. Drechsel, et al

鏈接：

https://www.nature.com/articles/s41586-019-1345-6

摘要：

直到最近，人類還和其他動物一樣，習慣於赤腳行走。因此，當人類走路時，腳底是身體和地面之間唯一的直接接觸。

這裡，我們證實，經常赤腳走路的肯亞人和美國人的腳底老繭比通常穿鞋走路的人更厚、更硬。然而，與鞋子不同的是，以硬度為衡量標準，老繭的厚度不會抵消行走過程中經歷的感知觸覺刺激頻率的能力。

此外，不像軟墊鞋，老繭的厚度不影響腳在走路時撞擊地面的力度。

Abstract

Until relatively recently, humans, similar to other animals, were habitually barefoot. Therefore, the soles of our feet were the only direct contact between the body and the ground when walking. Here we show that, as expected, people from Kenya and the United States who frequently walk barefoot have thicker and harder calluses than those who typically use footwear. However, in contrast to shoes, callus thickness does not trade-off protection, measured as hardness and stiffness, for the ability to perceive tactile stimuli at frequencies experienced during walking. Additionally, unlike cushioned footwear, callus thickness does not affect how hard the feet strike the ground during walking, as indicated by impact forces. Along with providing protection and comfort at the cost of tactile sensitivity, cushioned footwear also lowers rates of loading at impact but increases for ceimpulses, with unknown effects on the skeleton that merit future study.

天文/物理Astronomy/Physics

Reconstructing the late-accretion history of the Moon

重建月球晚期的吸積歷史

作者：Meng-Hua Zhu, Natalia Artemieva, Alessandro Morbidelli, et al

鏈接：

https://www.nature.com/articles/s41586-019-1359-0

摘要：

高親鐵元素（HSEs，即金、銥、鋨、鈀、鉑、錸、銠和釕）在追蹤行星形成晚期吸積階段方面的重要性早已得到公認。然而，月球吸積歷史的確切性質仍然是個謎。

這裡，我們進行了一系列的衝擊模擬來量化衝擊—保持比，然後利用蒙特卡羅方法考慮了單調衰減的衝擊通量，來計算在月球地殼和地幔歷史上吸積的衝擊質量。

我們發現，在月球整個撞擊史上，平均的撞擊物—留存率比之前估計的要低3倍左右。我們的結果表明，為了與月球地殼和地幔的HSE「收支」相匹配，HSEs的保留應該始於43.5億年前。而那時，大部分月球岩漿海洋已經凝固。

Abstract

The importance of highly siderophile elements (HSEs; namely, gold, iridium, osmium, palladium, platinum, rhenium, rhodium and ruthenium) in tracking the late accretion stages of planetary formation has long been recognized. However, the precise nature of the Moon"s accretional history remains enigmatic. Here we perform a series of impact simulations to quantify the impactor-retention ratio, followed by a Monte Carlo procedure considering a monotonically decaying impact flux, to compute the impactor massaccreted into the lunar crust and mantle over their histories. We find that the average impactor-retention ratio for the Moon"s entire impact history is about three times lower than previously estimated. Our results indicate that, to match the HSE budgets of the lunar crust and mantle, the retention of HSEs should have started 4.35 billion years ago, when most of the lunar magma ocean was solidified.

Tracking the precession of single nuclear spins by weak measurements

通過弱測量追蹤單個核自旋的旋進

作者：K. S. Cujia, J. M. Boss, K. Herb, J. Zopes & C. L. Degen

鏈接：

https://www.nature.com/articles/s41586-019-1334-9

摘要：

核磁共振（NMR）譜學是一種分析分子結構和功能，以及對其自旋密度進行三維成像的強大技術。

這裡，我們報告了利用周期弱測量對單核自旋旋進進行的追蹤。我們的實驗系統由金剛石中的核自旋組成。這些核自旋與附近氮空位中心的電子自旋弱相互作用，充當光學可讀的米量子位。我們觀察並使量子反作用力的兩個重要影響最小化：測量引起的退相干和與採樣時鐘的頻率同步。

我們利用周期性的弱測量來演示具有先驗未知頻率的多個核自旋的敏感、高解析度NMR波譜。該方法為實現單分子核磁共振的原子解析度提供了一條有效途徑。

Abstract

Nuclear magnetic resonance (NMR) spectroscopy is a powerful technique for analysing the structure and function of molecules, and for performing three-dimensional imaging of their spin densities. Here we report the tracking of single nuclear spin precession using periodic weak measurements. Our experimental system consists of nuclear spins in diamond that are weakly interacting with the electronic spin of a nearby nitrogenvacancy centre, acting as an optically readable meter qubit. We observe and minimize two important effects of quantum back-action: measurement-induced decoherence and frequency synchronization with the sampling clock. We use periodic weak measurements to demonstrate sensitive, high-resolution NMR spectroscopy of multiple nuclear spins with a priori unknown frequencies. Our method may provide a useful route to single-molecule NMR at atomic resolution.

糧食安全Food Security

National food production stabilized by crop diversity

農作物多樣性讓國家糧食生產保持穩定

作者：Delphine Renard & David Tilman

鏈接：

https://www.nature.com/articles/s41586-019-1316-y

摘要：

全球糧食需求增加、糧食儲備不足和氣候變化威脅著各國乃至全球糧食系統的穩定。和提高產量、灌溉以及作物對乾旱耐受性相關的政策已被提出作為增強糧食穩定的解決辦法。

這裡，我們評估了一種互補的可能性，即國家層面的作物更多樣化可能增加所有作物綜合起來的全國總收成的年復一年的穩定性。

我們利用50年來91個國家176種作物的年產量數據，檢驗了這一作物多樣性—穩定性假說。我們發現，在國家層面農作物更有效的多樣性，同全國總收成的時間穩定性的增加相關。

作物多樣性具有穩定作用，其大小與觀測到的降水變化的破壞穩定作用相似。這種更大的穩定性反映出收成急劇下降年份的頻率明顯較低。

Abstract

Increasing global food demand, low grain reserves and climate change threaten the stability of food systems on national to global scales. Policies to increase yields, irrigation and tolerance of crops to drought have been proposed as stability-enhancing solutions. Here we evaluate a complementary possibility—that greater diversity of crops at the national level may increase the year-to-year stability of the total national harvest of all crops combined. We test this crop diversity–stability hypothesis using 5 decades of data on annual yields of 176 crop species in 91 nations. We find that greater effective diversity of crops at the national level is associated with increased temporal stability of total national harvest. Crop diversity has stabilizing effects that are similar in magnitude to the observed destabilizing effects of variability in precipitation. This greater stability reflects markedly lower frequencies of years with sharp harvest losses.

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