Mechanistic studies of the plasma membrane block to polyspermy in mouse eggs

The mechanisms responsible for the plasma membrane associated block to polyspermy in mouse eggs were studied. Reinsemination experiments using zona-free eggs indicated that, after fertilization, the egg plasma membrane is altered such that sperm binding to the egg plasma membrane is blocked, except in the region of the second polar body. Activation of the egg with either ethanol or strontium chloride did not result in a block to polyspermic penetration, as artificially activated eggs displayed identical penetration levels as to nonactivated control eggs. The penetrability of activated eggs was not altered by the presence or absence of the zona pellucida during activation. Lectin staining for egg cortical granule material indicated that activation did cause cortical granule exocytosis; however, activated eggs remained penetrable. These data support the following conclusions: (1) an alteration in the ability of the egg plasma membrane to allow sperm adherence accounts for the block to polyspermy; (2) establishment of the plasma membrane block to polyspermy is sperm dependent, since artificial egg activation does not result in a block response; (3) the contents of the egg's cortical granules do not play a role in the establishment of the plasmalemma block response. © 1993 Wiley-Liss, Inc.     

A comparative study of the chemical analysis of ribs and femurs in woodland populations

Parallel chemical analyses of ribs and femurs from the Middle Woodland Gibson site and the Late Woodland Ledders site show that the elements most closely related to diet (strontium, zinc, magnesium) are found in identical proportions in the two bones. Elements associated with soil contamination (iron, aluminum, potassium, manganese) are found in a significantly higher proportion in the rib. The major elements calcium and sodium are found in lower levels in the ribs. Thus the rib is more sensitive to diagenetic processes that alter elemental proportions than is the femur. Conclusions concerning subgroupings by sex or site, derived from the diet-related elements (Sr, Zn, Mg), were found to be essentially the same for the rib and the femur.     

Effects of strontium on the absorption of calcium, magnesium and phosphate ions from the ovine reticulo-rumen

The net absorption rates of strontium ions from the ovine reticulo-rumen, isolated in situ in trained conscious animals, were measured under controlled conditions. A linear positive response was obtained from the addition of Sr²⁺ ions to the artificial rumen fluid. This increase in the absorption of Sr was reflected in an increase in the plasma Sr concentration. In contrast to the discrimination observed elsewhere in favour of the absorption of Ca relative to Sr, the absorption rate of Sr from the reticulo-rumen was significantly greater than that of Ca, from solutions containing the same molar concentration. A graded increase in the Sr concentration in the ruminal fluid from 1 mmol/l to 4 mmol/l led to a corresponding reduction in the absorption rate of Ca but an increase in that of phosphate. The latter result is similar to that observed when the intra-ruminal concentration of Ca²⁺ ions is increased. It is suggested that Ca and Sr share a common pathway for absorption from the reticulo-rumen and that this may involve coupling with the absorption of phosphate ions. Accepted: 18 January 2000     

Erosion and landscape development affect plant nutrient status in the Hawaiian Islands

We quantified variation in plant nutrient concentrations and provenance along catenas in landscapes of three different ages (0.15, 1.4, and 4.1 ma) in the Hawaiian Islands. Strontium (Sr) isotopes demonstrate that erosion provides a renewed source of rock-derived nutrients to slopes in landscapes of all ages, in some cases reversing a million years of ecosystem development in a distance of 100 m. However the effects of this input vary with landscape age. Plants on uneroded surfaces in a 0.15-ma landscape derive ~20% of their Sr from local bedrock (foliar ⁸⁷Sr/⁸⁶Sr~0.7085), while on adjacent slopes this increases to ~80% (foliar ⁸⁷Sr/⁸⁶Sr~0.7045). Despite this shift in provenance, foliar N and P do not vary systematically with slope position. Conversely, eroded slopes in a 4.1-ma landscape show smaller increases in rock-derived cations relative to stable uplands (foliar ⁸⁷Sr/⁸⁶Sr~0.7075 vs 0.7090), but have >50% higher foliar N and P. These results demonstrate both that erosion can greatly increase nutrient availability in older landscapes, and that the ecological effects of erosion vary with landscape age. In addition, there can be as much biogeochemical variation on fine spatial scales in eroding landscapes as there is across millions of years of ecosystem development on stable surfaces.     

Seawater strontium isotope curve at the Silurian/Devonian boundary: a study of the global Silurian/Devonian boundary stratotype

Present application of ⁸⁷Sr/⁸⁶Sr chemostratigraphy to detailed stratigraphical tasks is limited by inaccurate calibration of the general seawater strontium curve to absolute as well as to relative time scales. For this reason, refinement of the general seawater strontium curve has been suggested, using mainly clearly defined global boundary stratotype sections. This study reports the first ⁸⁷Sr/⁸⁶Sr data from the global Silurian/Devonian boundary stratotype section and fills an existing 1-Ma gap in available data. Generally, the data from the stratotype fit the range interpolated from published ⁸⁷Sr/⁸⁶Sr data of the general curve, but the slight differences may suggest an existence of a high-order oscillation near the Silurian/Devonian boundary. Higher ⁸⁷Sr/⁸⁶Sr values in the Devonian part of boundary bed 20 (20-beta) may indicate an exotic material influx of recycled sediment.     

Alkaline earth metal content of human bones at the site of «S'Illot des Porros» (Iron age,Mallorca, Spain)

The aim of this study is to establish the basic diet of the people inhumed at the site of Porros by analysing some of the alkaline earth metals present in human and animal bones. The site is a Talayotic necropolis established in the small island of «S'Illot des Porros» (Mallorca, Spain) during the 6th to 2nd century B.C. In this island the only evidence of human activity to be found is the necropolis; the corresponding settlement site is unknown. The results show that the diet of these people was based on a fundamentally marine economy perhaps mollusc collecting. This outcome agrees with a coastal location for the settlement site.     

Association of alkali metals and Alkaline-earth metals with the risk of schizophrenia in a Chinese population: A Case-Control study

Alkali metals (AMs) and alkali earth metals (AEMs) affect levels and signaling of neurotransmitters, which potentially play a role in the etiology of schizophrenia (SCZ). The current case-control study aims to explore how AMs [i.e. Potassium (K), sodium (Na), rubidium (Rb), cesium (Cs)] and AEMs [i.e. magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba)] in serum could associate with SCZ. One hundred and five inpatients with SCZ and 106 age- and sex-matched healthy controls (HCs) were recruited from Weifang, China. Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) was used to evaluate serum concentrations of Na, K, Ca, Mg and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was for Rb, Cs, Sr, Ba. Subjects with SCZ had significantly higher Mg and Sr serum concentrations than HCs (20.86 vs. 19.73 μg/mL of Mg, p < 0.001; 53.14 vs. 42.26 ng/mL of Sr, p < 0.001). After adjusting for confounders, the odds ratio of Mg and Sr remain significantly higher in the SCZ group (Mg: OR = 2.538, 95 % CI: 1.254–5.136, p=0.010; Sr: OR = 3.798, 95 % CI: 1.769–8.153, p = 0.001). No significant differences between SCZ subjects and HCs were observed for other AMs and AEMs. Higher serum concentrations of Mg and Sr were associated with SCZ. Studies are suggested to find the related mechanisms and provide clues for pathogenesis of SCZ, which would impact prevention and treatments of SCZ.     

关于锶同位素考古研究的几个问题

本文讨论了锶同位素考古研究所涉及的几个重要理论方法问题。首先是岩石、土壤和河流的锶同位素组成以及生物锶的来源问题。然后是锶同位素方法的四点局限性,即骨骼和牙本质样本的成岩污染问题、不同地区的锶同位素重叠现象、牙齿和骨骼的锶同位素混合效应和不能识别移民后代的问题。最后讨论了锶同位素方法应用于人类迁移研究的两个重难点,一是如何分辨一个遗址或墓地中的外来人口,二是如何找到外来人口的来源地。     

Simultaneous extension of both basic microstructural components in scleractinian coral skeleton during night and daytime,visualized by in situ 86Sr pulse labeling

Using in situ (12 h) pulse-labeling of scleractinian coral aragonitic skeleton with stable ⁸⁶Sr isotope, the diel pattern of skeletal extension was investigated in the massive Porites lobata species, grown at 5 m depth in the Gulf of Eilat. Several microstructural aspects of coral biomineralization were elucidated, among which the most significant is simultaneous extension of the two basic microstructural components Rapid Accretion Deposits (RAD; also called Centers of Calcification) and Thickening Deposits (TD; also called fibers), both at night and during daytime. Increased thickness of the ⁸⁶Sr-labeled growth-front in the RADs compared to the adjacent TDs revealed that in this species RADs extend on average twice as fast as TDs. At the level of the individual corallite, skeletal extension is spatially highly heterogeneous, with sporadic slowing or cessation depending on growth directions and skeletal structure morphology. Daytime photosynthesis by symbiotic dinoflagellates is widely acknowledged to substantially increase calcification rates at the colony and the corallite level in reef-building corals. However, in our study, the average night-time extension rate (visualized in three successive 12 h pulses) was similar to the average daytime extension (visualized in the initial 12 h pulse), in all growth directions and skeletal structures. This research provides a platform for further investigations into the temporal calibration of coral skeletal extension via cyclic growth increment deposition, which is a hallmark of coral biomineralization.     

青海喇家遗址人类遗骸的锶同位素比值分析

喇家遗址位于青海省民和县,主体为齐家文化的遗存,距今大约3900~4300年。喇家遗址古代人类迁移活动的研究,对于探索黄河上游古代文明,推动该地区齐家文化研究,有着积极的学术意义。本文首先采用电感耦合等离子体质谱技术对喇家遗址出土的22个个体的44份牙釉质和骨骼样品进行了元素分析,根据检测结果排除了受到污染的2份骨骼样品。其次,通过热电离质谱分析方法对喇家遗址出土22个个体的42份牙釉质和骨骼样品及8个猪牙釉质样品的锶同位素比值进行了测定。检测数据表明,猪牙釉质的锶同位素比值的标准偏差远小于其他动物,可以推断猪由当地饲养的可能性是最大的,因此其牙釉质锶同位素比值可以代表当地的锶同位素水平。经过计算得到8个猪牙釉质的锶同位素比值的平均值为0.710930,将该平均值加或减2倍标准偏差可以得到喇家遗址当地的锶同位素比值范围在0.711058~0.710802之间。以此为前提可以推测,本次检测的22个个体中,有17个个体牙釉质的锶同位素比值在遗址当地的锶同位素比值范围内,可能为本地出生。还有2个个体牙釉质在当地的锶同位素比值范围上下限附近,姑且存疑;仅有3个个体牙釉质的锶同位素比值在遗址当地的锶同位素比值范围以外,表明这些个体可能在其他地区出生,去世后埋葬在遗址中。此外,数据分析还显示,本地出生人群牙釉质的锶同位素比值平均值与骨骼的锶同位素比值平均值比较接近,暗示喇家遗址当地古人类生活方式可能比较统一。