CRYOANALYTICAL STUDIES OF FREEZING DAMAGE AND RECOVERY IN FUCUS VESICULOSUS (PHAEOPHYCEAE)

Receptacles of Fucus vesiculosus L. were examined using cryoscanning electron microscopy of rapidly frozen, hydrated tissue to avoid extraction and collapse of the extracellular matrix (ECM) and provide new structural information. The pore of the conceptacle was occluded by the tightly appressed tips of the paraphyses. These were embedded in copious ECM within the conceptacle. The ECM inside the conceptacle and in the medulla differed markedly in texture and with respect to the distribution of S and Cl, as revealed by energy-dispersive X-ray microanalysis. High levels of S were restricted to the conceptacle's ECM, whereas the ECM in the medulla was always S poor and Cl rich. Receptacles frozen naturally at low tide during the winter of 1998 showed extensive damage in the medulla, and this likely accounts for the cessation of reproduction during the winter on the Maine shore. The damaged receptacles recovered and resumed growth during the spring, and they released gametes by May. Abscission of the overwintered receptacles was observed in June to July, coincident with the formation of new receptacles at the tips of newly grown portions of the fronds.     

DOUBLE CONTRAST VISUALIZATION OF JOINTS

Double contrast arthrography, a method in which a dye and then oxygen is injected, can be used to visualize pathologic changes in the knee joint, that otherwise cannot be recognized preoperatively. In 28 cases in which the procedure was carried out there was no evidence of damage owing to it.This method is worthy of consideration for visualization of conditions in the shoulder joint, hip, or any joint having a distensible cavity.     

FREEZING POINTS OF ANTI-COAGULANT SALT SOLUTIONS

By a method involving equilibration of ice and solution, and analysis of the solution, freezing point depressions of solutions of sodium citrate, oxalate, and fluoride have been determined over the range Δ = 0.45 to 0.65°C. Determinations with sodium chloride solutions have confirmed the accuracy of the method. In each case the freezing point depression is given, within 0.002°C., as a linear function of the concentration. By the use of these linear equations it is possible to prepare a solution of any of these four salts isotonic with a given biological fluid of known freezing point, provided the latter falls within the range studied.     

长白山树木的耐冻性

本文应用低温冰箱冷冻,水培观察生活力的方法研究了长白山51种树木越冬一年生枝条的耐冻性,目的在于探讨树木耐冻性和海拔分布之间的关系,为进一步开展树木越冬伤害形式及适应性研究提供基础资料。 材料与方法 1984年和1985年10月初树木落叶后,从天然林中剪取树木一年生枝条,贮于室外背荫处。次年1—2月(预计深休眠期已过),可进行耐冻性测定。     

IN FAVOUR OF FREEZING EGGS FOR NON-MEDICAL REASONS

This article explores the social benefits and moral arguments in favour of women and couples freezing eggs and embryos for social reasons. Social IVF promotes equal participation by women in employment; it offers women more time to choose a partner; it provides better opportunities for the child as it allows couples more time to become financially stable; it may reduce the risk of genetic and chromosomal abnormality; it allows women and couples to have another child if circumstances change; it offers an option to women and children at risk of ovarian failure; it may increase the egg and embryo pool. There are strong arguments based on equal concern and respect for women which require that women have access to this new technology. Freezing eggs also avoids some of the moral objections associated with freezing embryos.     

13种木兰科树种叶片解剖与其抗寒性

供试的黄心夜合(Michelia martinii)等抗寒性较强的木兰科树种叶片结构特征是:叶片单位面积气孔密度小,上表皮角质膜厚度大和叶肉栅栏组织发达。     

亚硫酸对PSII的伤害

从菠菜叶中提取 PSII 颗粒和叶绿体、经亚硫酸处理后发现:由 PSII 颗粒催化的 DCIP光还原速率依 SO_3~(2-)浓度增高而降低、伤害部位发生于 PSII 的氧化侧,接近水的部位。在黑暗条件下 H_2O→DCIP 和 DPC→DCIP 的电子传递均不受影响。在特定 SO_3~(2-)浓度下,PSII 颗粒的伤害随处理时间的延长而加重,其伤害机理与33kD 多肽的解离和 Mn 的流失有关。SO_3~(2-)对新鲜叶绿体并不伤害;对老化的叶绿体则伤害明显,DCIP 光还原速率依老化时间的延长而降低。Mn 含量的减少与 DCIP 光还原速率的降低呈正相关,试样中添加 EGTA后电子传递速率受害更为严重。