ORGANIZATION AND REPLICATION ACTIVITY OF THE MITOCHONDRIAL MASS OF OOGONIA AND PREVITELLOGENIC OOCYTES IN XENOPUS LAEVIS

The origin of the mitochondrial mass, previously well characterized in Xenupus diplotene oocytes, has been traced up to oogonia by means of electron microscopy. A polarized organization of the oogonia and of the oocytes of the succeeding stages was observed. The mitochondrial cloud was found to be built up in the centriolar region near the site where the chromosomes will be implanted along the nuclear envelope at the "bouquet" stage. Autoradiographic studies of thymidine incorporation into mitochondrial DNA suggest that mitochondrial DNA synthesis is active throughout this early period of oogenesis.     

牛脾转移因子的提取工艺研究

目的：比较从牛脾中提取活性ＴＦ的不同方法。方法：分别利用Ｌａｗｒｅｎｃｅ－－透析法、Ｌａｗｒｅｎｃｅ－超滤法、超离心－超滤法提取,再以蛋白反应、红外及紫外扫描予以鉴定比较。结果：Ｌａｗｒｅｎｃｅ－超滤法和超离心－超滤法效果较好。结论：工业化生产中应采用Ｌａｗｒｅｎｃｅ－超滤法。     

Systematics of the extinct reed warblers Acrocephalus of the Society Islands of eastern Polynesia

In the Society archipelago (French Polynesia), Acrocephalus reed warblers are known only from four islands: Tahiti, Mo'orea, Huahine and Raiatea. All populations are now extinct except on Tahiti. Our knowledge of these birds is based on a small number of specimens preserved in museums, collected mostly during the 19th century. We present here a review of the past and present distribution, habitat and threats to the Society Islands reed warblers, including details on the specimens in museum collections. We compare the external morphology of the different populations, and use samples from museum specimens to propose a molecular phylogeny of all taxa based on partial cytochrome b gene sequences. The genetic data do not support the monophyly of the Society Islands reed warblers, which probably derived from three different lineages, found in Tahiti, Mo'orea and in the cluster Raiatea–Huahine. We outline the taxonomic consequences of this phylogeny. Our results support the hypothesis that evolutionary pattern, not distance between islands, shaped the long-distance colonization of oceanic islands by reed warblers.     

Functional diversity of reef molluscs along a tropical-to-temperate gradient

Coral Reefs - Global warming is leading to range shifts of marine species, threatening the structure and functioning of ecological communities and human populations that rely on them. The largest...     

Vice-anvil use in nut processing by two Corvus species

Woodpeckers and certain passerine species secure encased food in the environment in various ways to facilitate the extraction of the contents with their bills. They do this by securing the food items in locations such as crevices and holes, newly defined in this paper as ‘vice-anvils’. Here I report that free-living New Caledonian crows (Corvus moneduloides) and rooks (Corvus frugilegus, in New Zealand) also use vice-anvils to process candlenuts and walnuts, respectively. New Caledonian crows placed candlenut sections in vice-anvils to aid kernel extraction, after the candlenuts had been dropped onto an anvil to break them open. In contrast, rooks used vice-anvils to secure walnuts while they broke the shell with their bills. Long-term use by rooks of a vice-anvil in a tree had produced a ‘purpose-made’ nut-cracking site. My findings extend the persistent use of specific vice-anvils to Corvus species and further demonstrate their innovative and flexible foraging behaviour.     

Phylogenetic relationships among prokaryotic and eukaryotic catalases

Seventy-four catalase protein sequences, including 29 bacterial, 8 fungal, 7 animal, and 30 plant sequences, were compiled, and 70 were used for phylogenetic reconstruction. The core of the resulting tree revealed unique, separate groups of plant and animal catalases, two groups of fungal catalases, and three groups of bacterial catalases. The only overlap of kingdoms occurred within one branch and involved fungal and bacterial large-subunit enzymes. The other fungal branch was closely linked to the group of animal enzymes. Group I bacterial catalases were more closely related to the plant enzymes and contained such diverse taxa as the Gram-positive Listeria seeligeri, Deinocococcus radiodurans, and gamma-proteobacteria. Group III bacterial sequences were more closely related to fungal and animal sequences and included enzymes from a broad range of bacteria including high- and low-GC Gram positives, proteobacteria, and a bacteroides species. Group II was composed of large-subunit catalases from diverse sources including Gram positives (low-GC Bacilli and high-GC Mycobacteria), proteobacteria, and species of the filamentous fungus Aspergillus. These data can be interpreted in terms of two gene duplication events that produced a minimum of three catalase gene family members that subsequently evolved in response to environmental demands. Horizontal gene transfer may have been responsible for the group II mixture of bacterial and fungal large-subunit catalases.      

Comparison between Ageing of Slices and Ethylene or Rindite Treatments of Whole Potato Tubers: Studies on Microsomal and Mitochondria1 Enzymatic Activities

When potato tubers (Solanum tuberosum L.) are treated with Rindite(ethylene chlorohydrin, ethylene dichloride, carbon tetrachloride,7/3/1, v/v/v) for 2 d, and then stored at 20°C, importantchanges in enzymatic activities are observed in mitochondrialas well as in microsomal fractions isolated from these tubers.In mitochondria isolated from Rindite-treated tubers, the oxidationofsuccinate was more active and more resistant to cyanide thanin mitochondria from untreated tubers. The functioning of acyanide-resistant, SHAM-sensitive oxidative activity was similarto that observed after an ageing treatment of tuber slices oran ethylene treatment of whole tubers. However, in the lattercase, changes in oxidative properties or cyanide-resistancewere less important. Moreover, all the observed changes disappearedafter 4 d of storage. The NADH-femcyanide reductase and NADHcytochromec reductase activities of microsomal fractions isolated fromRindite-treated tubers increased after 1 d or 4 d of storage,relative to the activities of untreated tubers. Moreover, theoleatedesaturase activity, which could not be detccted in microsomesprepared from untreated tubers, was high in microsomes fromtreated tubers stored for 1 d and 4 d, and then the activitydecreased. The induction of an oleatedesaturase activity byRindite treatment can be compared to the effect of the ageingtreatment on tuber slices. The enhancement of oleatedesaturaseactivity was linked to an increase in cytochrome b5content ofmicrosomes of treated tubers. However, all these changes werenot observed when whole tubers were treated with ethylene alone. Key words: Rindite, Mitochondria, Microsomes, Solanum tuberosum     

Changes of DNA Ligases in Chick Neural Retina as a Function of Age

In the course of chick neural retina development, several forms of DNA ligase have been found. During embryonic life the major DNA ligase activity that is found at seven days is form I (8.2 S) which gradually decreases and disappears by 14 days after incubation, whereas form II (6.2 S) increases to reach a maximum at the time of hatching. Form II then decreases reaching a constant level by Day 7 and from that time new slow sedimenting forms also appear (forms III and IV). Form III (2 S) is first detectable at seven days and increases up to 90 days, whereas form IV (3 S) is the only form detected in the 17- and 18-month-old and also in the 5-year-old birds. These four forms display different elution patterns on phosphocellulose column chromatography. They also differ in their thermal stability and sensitivity towards N-ethylmaleimide.     

Membrane lipids and ethanol tolerance in the mouse. The influence of dietary fatty acid composition

Mice of the TO Swiss strain received diets containing different amounts of saturated or unsaturated fat throughout life. These diets produced characteristic changes in cardiac phospholipid fatty acid composition, but produced no significant differences in fatty acid composition of phospholipids from a crude membrane fraction of brain. When littermates of these animals were exposed to ethanol vapour in an inhalation chamber it was observed that mice which had received a diet high in saturated fat lost the righting reflex at an estimated concentration of ethanol in blood higher than that required for mice receiving a control diet, or a diet rich in polyunsaturated fat. Analysis of the brain membrane fraction from those animals which had received ethanol revealed that mice receiving the highly saturated fat diet now had a significantly greater proportion of saturated fatty acids in brain membrane phospholipids. These results are discussed in relation to the hypothesis that brain membrane lipid composition may influence the behavioural response to ethanol.