Asymmetric effects of daytime and nighttime warming on alpine treeline recruitment

Trees at their upper range limits are highly sensitive to climate change, and thus alpine treelines worldwide have changed their recruitment patterns in response to climate warming. However, previous studies focused only on daily mean temperature, neglecting the asymmetric influences of daytime and nighttime warming on recruitments in alpine treelines. Here, based on the compiled dataset of tree recruitment series from 172 alpine treelines across the Northern Hemisphere, we quantified and compared the different effects of daytime and nighttime warming on treeline recruitment using four indices of temperature sensitivity, and assessed the responses of treeline recruitment to warming-induced drought stress. Our analyses demonstrated that even in different environmental regions, both daytime and nighttime warming could significantly promote treeline recruitment, and however, treeline recruitment was much more sensitive to nighttime warming than to daytime warming, which could be attributable to the presence of drought stress. The increasing drought stress primarily driven by daytime warming rather than by nighttime warming would likely constrain the responses of treeline recruitment to daytime warming. Our findings provided compelling evidence that nighttime warming rather than daytime warming could play a primary role in promoting the recruitment in alpine treelines, which was related to the daytime warming-induced drought stress. Thus, daytime and nighttime warming should be considered separately to improve future projections of global change impacts across alpine ecosystems.     

硫酸铝钾对小鼠肝损害的实验研究

本文主要观察硫酸铝钾——饮用水净化剂引致小鼠肝酶组化,超微结构和组织结构的变化。动物30只,分为正常组、硫酸铝钾大、小剂量组。实验结果:硫酸铝钾10mg/kg/日(大剂量组)与5mg/kg/日(小剂量组)动物用药10天、80天均可使肝SDH酶活性降低;肝细胞线粒体肿胀、嵴断裂和溶解。在光学显微镜下用药80天后大部分肝细胞肿胀,胞浆疏松淡染、肝小叶内可见呈小灶状分布的炎性细胞浸润,主要为淋巴细胞及浆细胞,门管区偶见少许炎性细胞,但肝小叶和门管区未见结缔组织增生。为此,硫酸铝钾作为净水剂,不宜用量过大。     

体外冲击波碎石术对兔肝酶活性的影响

采用超微组织化学方法,观察了体外冲击波碎石术(ESWL)对家免肝脏酶活性的影响。实施 ESWL 后,肝细胞的琥珀酸脱氢酶(SDH)和毛细胆管壁上的碱性磷酸酶(ALP)、焦磷酸硫胺素酶(TPPase)反应活性减弱或消失。TPPase 从损伤的肝细胞高尔基体分泌面扁囊、溶酶体样小泡和毛细胆管内溢出,并伴有肝细胞面的质膜上出现了 TPPase 反应产物和形成膜包内凹小泡。结果提示 ESWL 可对肝细胞及毛细胆管的功能和结构有损伤作用。     

Mortality rates of desert vegetation during high-intensity drought at Uluru-Kata Tjuta National Park,Central Australia

Precipitation variability and heatwaves are expected to intensify over much of inland Australia under most projected climate change scenarios. This will undoubtedly have impacts on the biota of Australian dryland systems. However, accurate modelling of these impacts is presently impeded by a lack of empirical research on drought/heatwave effects on native arid flora and fauna. During the 2018–2021 Australian drought, many parts of the continent's inland experienced their hottest, driest period on record. Here, we present the results of a field survey in 2021 involving indigenous rangers, scientists and national parks staff who assessed plant dieback during this drought at Ulur u-Kata Tjut a National Park (UKTNP), central Australia. Spatially randomized quadrat sampling of eight common and culturally important plants indicated the following plant death rates across UKTNP (in order of drought susceptibility): desert myrtle (Aluta maisonneuvei subsp. maisonneuvei) (91%), yellow flame grevillea (Grevillea eriostachya) (79%), Maitland's wattle (Acacia maitlandii) (67%), waxy wattle (A. melleodora) (65%), soft spinifex grass (Triodia pungens) (53%), mulga (A. aneura) (42%), desert oak (Allocasuarina decaisneana) (22%) and quandong (Santalum acuminatum) (0%). The sampling also detected that seedling recruitment was absent or minimal for all plants except soft spinifex, while a generalized linear mixed model (GLMM) indicated two-way interactions among species, plant size and stand density as important predictors of drought survival of adult plants. A substantial loss of biodiversity has occurred at UKTNP during the recent drought, with likely drivers of widespread plant mortality being extreme multi-year rainfall deficit (2019 recorded the lowest-ever annual rainfall at UKTNP [27 mm]) and record high summer temperatures (December 2019 recorded the highest-ever temperature [47.1°C]). Our findings indicate that widespread plant death and extensive vegetation restructuring will occur across arid Australia if the severity and frequency of droughts increase under climate change.     

Melanization Stimulating Activity in the Skin of the Gilthead Porgy,Sparus auratus

The presence of a melanization-stimulating factor (MSF) was discovered in dorsal and/or ventral skin of Sparus auratus. Skin from this marine species was used to condition Steinberg's balanced salt solution (BSS), which was subsequently tested with the neural tube assay. BBS conditioned by dorsal and/or ventral skin of S. auratus at 25% and 50% concentrations had a profound stimulatory effect on the percentage of melanization of neural crest cells throughout the 3day assay period. In some cases 90% melanization occurred within the first 24 hr. Such stimulated cells showed a doubling of the number of dendrites per cell. assess the effects of MSF on other indices of melanization, dorsal and/or ventral skin was used to condition MEM used in the culture of B16-F10 murine melanoma cells. During the first 24 hr, B16-F10 murine melanoma cells responded to conditioned media by demonstrating a considerable increase in activities of tyrosine hydroxylase, dopa oxidase, and dopachrome tautomerase, but no effect was observed on melanin content. In contrast, melanin content increased after 48 hr of incubation, whereas the enzymatic activities were inhibited during this period. It seems that MSF activity, expressed in several ways, may be present generally among marine species.     

Buoyancy variations in eggs of Atlantic cod (Gadus morhua L.) in relation to chorion thickness and egg size: theory and observations

Egg specific gravity is a function of egg volume, chorion volume, perivitelline space (PVS) and the specific gravity of chorion and ovoplasm. Experimental studies on cod ( Gadus morhua L.), a marine multiple batch spawner, showed that approx. forty per cent of the chorion volume is incorporated between batches and that the chorionic material has a mean specific gravity of 1·20 (range: 1·14–1·35). The chorion volume and specific gravity are low at the end of the spawning period in extremely fecund fish. Specific gravity of ovoplasm was observed to be 1·017 in marine eggs and calculated to be about 1·008 in brackish water eggs. Inherent variation in PVS is found to have little influence on egg specific gravity. With the other variables constant, egg specific gravity is inversely related to egg volume supported by studies on single batches of eggs. Measurements on every batch of eggs reveal that the production of large eggs (>1·3 mm) gives low density eggs initially and high density eggs towards the end of spawning, while the production of small eggs (<1·3mm) gives moderate specific gravity. These observations are discussed in relation to vertical distribution of the eggs and reproductive success of recruit and repeat spawners. There are indications that repeat spawners produce larger eggs.     

LIFE CYCLE OF A STEPHANODISCUS SP. (BACILLARIOPHYTA)1

Studies of the life cycle of a centric diatom, tentatively identified as Stephanodiscus neoastraea Håkansson & Hickel, showed that sexual reproduction occurred every year in a freshwater lake (Lough Neagh, Northern Ireland). Male and female gametes were produced in cells below 55% of the maximum diameter during a 3–4-week period in late summer, following the return of nitrate concentrations above 10 μM NO_3-N. The frequency of sexual reproduction was linked to the cycle of diameter size reduction and regeneration. The times of largest decreases in cell diameter were during nutrient stress in summer and low light conditions in late autumn, rather than during the main spring growth period. So, environmental conditions (combined with the limited life-spans of individual cells) affected the rate of diameter reduction and, therefore, the length of the life cycle (3–4 years).     

Stock and recruitment and inversely density-dependent growth of salmon, Salmo salar L., in a Scottish stream

For the 6 years for which detailed data are readily available, estimates of the survival of emergent fry of Atlantic salmon, Salmo salar L., to the first and second autumns at a site on the Shelligan Burn are consistent with the dome-shaped Ricker model with about 11 emergent fry m⁻² maximizing recruitment. The data are not satisfactorily fitted by the asymptotic Beverton and Holt model. A possible mechanism, which results from the observed inversely density-dependent growth, is discussed briefly.     

尿素氮-葡萄糖双功能分析仪的研究

由固定化脲酶、谷氨酸脱氢酶、谷氨酸氧化酶、葡萄糖氧化酶的复合酶膜组成的双电极系统,可以同时测定尿素氮和葡萄糖的含量,每次进样量为25μl,20s即可测定出尿素氮和葡萄糖的含量。在0～60mg/dl尿素氮、0～500mg/dl葡萄糖范围内具有良好的线性关系。连续测定20次的变异系数分别为1.02％和1.05％。酶膜使用寿命为两星期以上。此仪器可广泛应用于临床检验和体育训练中。