Grain-size controls on the occurrence of bioturbation

Grain size and grain-size related stresses impart a significant influence on the ichnological character of marginal-marine deposits. This is evident on the New Brunswick coastline of the Bay of Fundy, Canada, where three coarse-grained marginal-marine deposits are studied to assess grain-size controls on the occurrence and type of bioturbation. Firm mud and sand substrates exhibit the greatest diversity and density of bioturbation (i.e., bioturbation intensity). The types of organisms colonizing sands and firm-mud substrates are variable; however, the resultant trace assemblages are similar. Thixotropic muds exhibit significantly reduced trace diversity and density relative to firm mud, reflecting the additional stress placed on the organisms by the relatively soupy consistency of the sediment. A significant change in the trace assemblage occurs when sediment caliber passes the gradational sand—fine gravel boundary.Four main conclusions can be drawn from this study. First, for mixed sand and gravel, fine gravel, and coarse-gravel deposits, the degree of bioturbation (diversity ^? density) decreases more rapidly onshore (across the intertidal zone) than is noted in sand or mud deposits. Second, there is a decrease in the degree of bioturbation with increasing grain size for substrates composed of sand-sized and larger clasts. Third, burrows in gravels tend to be lined and/or robust, likely to maintain a stable environment within the burrow. Fourth, in coarse-gravel substrates or substrates with a significant component of coarse gravel, burrows are developed between the clasts and tend to be more permanent structures (than those developed in sand or mud), which are generally continuously occupied.The degree of burrowing noted in these modern gravel deposits contrasts with the relative paucity of biogenic structures reported in conglomerates preserved in the rock record. Based on the intensity of burrowing observed in the gravels, we hypothesize that ancient marginal-marine conglomerates are likely bioturbated, but that these burrows are likely distorted during burial and compaction.     

Structural characterization of the partially folded intermediates of an immunoglobulin light chain leading to amyloid fibrillation and amorphous aggregation

Immunoglobulin light chain deposition diseases involve various types of extracellular deposition of light chain variable domains, including amyloid fibrils and amorphous deposits. The decreased thermodynamic stability of the light chain is believed to be the major factor leading to fibrillation. However, the differences in the nature of the deposits among the light chain deposition diseases raise the question of whether the mechanisms leading to fibrillar or amorphous aggregation is different. In this study, we generated two partially folded intermediates of the light chain variable domain SMA in the presence of guanidine hydrochloride (GuHCl) and characterized their conformations. The more unfolded intermediate formed fibrils most rapidly, while the more native-like intermediate predominantly led to amorphous deposits. The results also show that the monomeric, rather than the dimeric state, was critical for fibrillation. The data also indicate that fibril elongation involves addition of a partially unfolded intermediate, rather than the native state. We postulate that a more highly unfolded intermediate is more suited to undergo the topological rearrangements necessary to form amyloid fibrils than a more structured one and that this also correlates with increased destabilization. In the case of light chain aggregation, it appears that more native-like intermediate conformations are more prone to form amorphous deposits.     

A demonstration of the advantages of immunostaining in the quantification of amyloid plaque deposits

Extracellular amyloid deposits are a feature of both Alzheimer type dementia and the 'normal' aging process. Quantification of amyloid plaque deposits may well be useful in distinguishing between the senescent changes associated with 'normal' aging and the pathological processes underlying dementia. To determine the most reliable and reproducible method for visualisation of the amyloid we have compared conventional silver staining techniques with beta-amyloid immunocytochemistry on a large sample of post-mortem brain tissue from both demented (n = 15, age range 60-87) and non-demented (n = 65, age range 14-99) patients. The degree of amyloid deposition was rated on a four point scale and ratings for the two techniques were significantly correlated (P less than 0.01). However, the immunocytochemical approach has a number of distinct advantages for quantification. The antibody to beta-amyloid is highly specific and does not stain neurofibrillary tangles or background features, it is considerably more sensitive than silver staining in highlighting diffuse amyloid deposits and, perhaps most importantly, it produces high contrast staining which allows easier image digitisation and subsequent computer image analysis.     

Calcium carbonate deposits reduce predation pressure on Gammarus fossarum from salamander larvae

• 1 We studied the lime deposits on Gammarus fossarum from a tufa brook in Southern Germany. Between 20 and 75% of the gammarids collected carried calcium carbonate deposits at the dorsal part of the pleon segments. Average weight of deposits ranged between 0.6 mg on small and 1.7 mg on large specimens and constituted 60–20% of specimens' dry weights.
• 2 Predator‐prey experiments with salamander larvae and gammarids showed that significantly fewer prey with deposits were eaten than without deposits and that the differences in predation risks between prey with vs. prey without deposits were greatest in small and medium sized specimens.
• 3 Lime deposits changed the feel or taste and the activity patterns of gammarids. Gammarids with deposits were rejected significantly more often by the predators than gammarids without deposits. Medium sized specimens with deposits, which suffered a great predation risk, were significantly less active than specimens of the same size category without deposits.
• 4 Lime deposits did not increase conspicousness or decrease escape ability of prey. Prey with deposits were attacked by predators with the same frequency and captured with the same success as prey without deposits.
• 5 Lime deposits may afford effective protection from salamander predation in some natural habitats. Predation impact on gammarids by salamander larvae may be low, however, because larval density was very low in most places (< 1 m^‐2) and because larvae are only present for a limited time until they start metamorphosis.

     

Scent‐Mark Identification and Scent‐Marking Behaviour in African Wild Dogs (Lycaon pictus)

Scent‐marking is common in mammals, but where signals are carried by urine and faeces, distinguishing between scent‐marking and mere elimination is problematic. To do so, we documented behaviours and context variables associated with urination and defecation in free‐ranging endangered African wild dogs (Lycaon pictus) and tested whether these were related to the responses of other dogs to deposits. We found that distinct postures were almost uniquely associated with deposits by dominant wild dogs, were more common during urination than defecation, and increased the likelihood that these deposits would be investigated by other wild dogs. The likelihood of investigation depended on the sex and dominance status of the depositor, the type of deposit and the substrate. Urine from dominant females was more likely to be investigated by other wild dogs than any other deposits, and deposits placed on vegetation were more likely to be investigated than those on bare ground. The likelihood that a deposit would be overmarked was affected by the deposit type and the sex and dominance status of the last depositor. Collectively, these results suggest that dominant wild dog urine is of greatest interest to other dogs. Our results show that some deposits by African wild dogs are not scent‐marks and that detailed observations of behaviours and context variables during elimination events can be used to distinguish deposits that are likely to be of communication value.     

Mercury-biogeochemical exploration for mineral deposits

Biogeochemical prospecting for mercury deposits and deposits of other minerals by the chemical analysis of mercury in plants or plant tissue that accumulate this element in linear (or near linear) proportion to the concentration in the soil is an effective method of exploration, even where allochthonous material as much as 200 to 2000 m thick covers the deposits. Plant tissues with this tendency to accumulate mercury (designated as non-barrier to mercury) comprise only a small fraction of the total of 255 types of plant tissues that were tested. Ten of these were considered to be quantitatively informative, and their mercury concentrations exceeded background values 300 or more times. The remaining types of plant tissues ranged in prospecting value from semi-quantitatively informative to qualitatively informative to uniformative (mercury values at or below background). The failure of some earlier uses of this prospecting method is attributed to the use of inappropriate plant tissues, to the mercury in the particular substrate studied existing in a form of low mobility and availability to plants, or to both causes.Prospecting by examining mercury concentrations in soils and rocks (lithogeochemical prospecting) is more effective than the biogeochemical approach only in prospecting for cinnabar deposits having no allochthonous cover. Mercury-biogeochemical prospecting is most effective for non-mercury mineral deposits and for oil and gas deposits. The types of plant tissues used in these studies are listed and are classified according to their value in prospecting. A case history is given of the Ozernoe pyrite-polymetallic deposit in Siberia.     

Facies characteristics and diversity in carbonate eolianites

Carbonate eolian dunes can form huge sand bodies along the coasts but are seldom described in the pre-Quaternary record. The study of more than 600 thin-sections collected in present-day, Holocene and Pleistocene dunes from Sardinia, Crete, Cyprus, Tunisia, Morocco, Australia and Baja California confirms that these deposits can be easily misinterpreted as shallow marine at core or thin-section scale. The classical eolian criteria (fine-grained and well-sorted sands) are exceptional in carbonate dunes because the diversity of shapes and densities of carbonate particles lowers the critical shear velocity of the sediment thus blurring the sedimentary structures. Wind carbonate deposits are mainly heterogeneous in size and often coarse-grained. The paucity of eolianites in the pre-Quaternary record could be due to misinterpretation of these deposits. The recognition should be based on converging sedimentological and stratigraphic elements at core scale, and diagenetic (vadose diagenesis, pedogenetic imprints) and petrographical (grain verticalization, scarcity of micritic envelopes, broken and/or reworked foraminifera) clues in thin-section. Bioclastic or oolitic grainstones showing evidence of vadose diagenesis or pedogenetic imprints, should always be suspected of having an eolian origin.     

论华北旧石器晚期遗址的分布、埋藏以及地质时代问题

我国华北地区旧石器晚期遗址及文化遗物通常埋藏于河流的第二级阶地中,地质时代为晚更新世中、晚期。峙峪等遗址的地层清晰、化石丰富、时代明确,没有再搬运的任何迹象。研究旧石器文化必须结合地层、地貌和古生物资料进行综合分析,有适当的年龄数据印证,才能得出断代上的合乎逻辑的结论。     

Re-appraisal of the stratigraphy and determination of new U-Pb dates for the Sterkfontein hominin site, South Africa

Sterkfontein Caves is the single richest early hominin site in the world with deposits yielding one or more species of Australopithecus and possible early Homo, as well as an extensive faunal collection. The inability to date the southern African cave sites accurately or precisely has hindered attempts to integrate the hominin fossil evidence into pan-African scenarios about human evolutionary history, and especially hominin biogeography. We have used U-Pb and U-Th techniques to date sheets of calcium carbonate flowstone inter-bedded between the fossiliferous sediments. For the first time, absolute age ranges can be assigned to the fossil-bearing deposits: Member 2 is between 2.8 ± 0.28 and 2.6 ± 0.30 Ma and Member 4 between 2.65 ± 0.30 and 2.01 ± 0.05 Ma. The age of 2.01 ± 0.05 Ma for the top of Member 4 constrains the last appearance of Australopithecus africanus to 2 Ma. In the Silberberg Grotto we have reproduced the U-Pb age of ∼2.2 Ma of for the flowstones associated with StW573. We believe that these deposits, including the fossil and the flowstones, accumulated rapidly around 2.2 Ma. The stratigraphy of the site is complex as sediments are exposed both in the underground chambers and at surface. We present a new interpretation of the stratigraphy based on surface mapping, boreholes logs and U-Pb ages. Every effort was made to retain the Member system, however, only Members 2 and 4 are recognized in the boreholes. We propose that the deposits formally known as Member 3 are in fact the distal equivalents of Member 4. The sediments of Members 2 and 4 consisted of cone-like deposits and probably never filled up the cave. The U-Th ages show that there are substantial deposits younger than 400 ka in the underground cave, underlying the older deposits, highlighting again that these cave fills are not simple layer-cakes.     

A method for marking the position of nichrome microelectrode tips in nervous tissue

A method for revealing nickel deposits from nichrome microelectrodes in the mammalian central nervous system is described. These deposits are stained red by dimethylglyoxime and can be observed directly or in Nissl stained sections. This method allows one to identify the exact position of a nichrome electrode in a microelectrode bundle chronically implanted in the brain.     

Developmental changes in the localization of calcium binding sites inAcanthamoeba castellanii

Summary Vegetative cells ofAcanthamoeba castellanii have the ability to bind calcium on the plasma membrane in form of the electron-dense deposits. The appearance of the deposits depends on the age ofAcanthamoeba culture. In 24-h-old culture the deposits are very small, with diameter of 26 nm. During aging of culture, at both logarithmic and stationary growth phases, the diameter of deposits is larger (70–80 nm), while the deposits are localized only on the plasma membrane. During differentiation ofAcanthamoeba cells into cysts electron-dense deposits with a diameter of about 170 nm appear in the mitochondria, whereas no deposits are observed on the plasma membrane. However, at the first stage of differentiation electron-dense material together with extruded membraneous fragments are also observed outside of some newly-formed young cysts. These results suggest that inAcanthamoeba cells, depending on the stage of life cycle, either plasma membrane or mitochondria may be involved in storage of excess cellular calcium.     

The saprotrophic bacterial complex in the raised peat bogs of Western Siberia

The population density of bacteria in peat deposits along the landscape profile of the Vasyugan Marsh has been found to be as high as tens of millions of CFU/g peat. The abundance and diversity of bacteria increased with depth within the peat deposit, correlating with an increasing level of peat degradation. Variations in these parameters with depth and season were greater in peat deposits located in transaccumulative and transitional positions than in the sedge-sphagnum bogs located at the eluvial region of the profile. In the upper 1-m-thick layer of the peat deposits studied, bacilli, represented by five species, dominated, whereas, in the deeper layers, spirilla and myxobacteria prevailed. These bacteria were major degraders of plant polymers. Unlike the bacterial communities found in the peat deposits of European Russia, the dominant taxa in the studied peat deposits of Western Siberia are represented by bacteria resistant to extreme conditions.     

A Method for Marking the Position of Nichrome Microelectrode Tips in Nervous Tissue

A method for revealing nickel deposits from nichrome microelectrodes in the mammalian central nervous system is described. These deposits are stained red by dimethylglyoxime and can be observed directly or in Nissl stained sections. This method allows one to identify the exact position of a nichrome electrode in a microelectrode bundle chronically implanted in the brain.     

Toxic Element Levels in the Phosphate Deposits of Central Jordan

The phosphate deposits are used mainly as raw materials in the fertilizer industry. However, toxic elements content in both phosphate ores and final mining products has received little attention. The present study used inductively coupled plasma mass spectrometry (ICP-MS) to determine levels of toxic elements in phosphate deposits in Al-Hisa and Al-Abyad mines, Jordan. Concentrations of elements were converted into rock content based on the ICP-MS results and compared using an enrichment-factor (EF) method that normalized to the mean concentration of elements in crustal rock. The results showed that the U, V, and Hg were enriched in the Jordanian deposits compared to the average worldwide phosphate (AWP), whereas lower enrichments of Pb were found in the Jordanian deposits (JP). Other trace elements had similar levels in Jordanian deposits comparable to worldwide averages of phosphates. Concentrations of U, V, and Cd in Jordanian phosphate deposits were greater than the permissible limits for soils for growing crops established by the European Community (EC) and World Health Organization (WHO). Finally, Jordanian phosphate deposits show the highest enrichment of Hg and U, thus can be regarded as U-bearing.     

水稻雌蕊与胚囊中钙的超微细胞化学定位

用焦锑酸盐沉淀法对水稻（OryzasativaL．）授粉前后雌蕊和胚囊中的钙进行了超微细胞化学定位。结果表明,柱头乳突细胞表面和花柱薄壁细胞中均含钙沉淀;开花前1d,整个胚囊中含钙较少,两个助细胞中钙分布无差异;临近开花时,1个助细胞已退化,其钙含量明显增加;开花后6h,胚囊已受精,退化助细胞中钙含量进一步增加;受精前卵细胞中钙主要分布在液泡中,核和胞质中较少;受精后,其钙含量明显增加,主要分布于核中。重点讨论了钙与助细胞退化和卵细胞激活的关系。     

Comparison of intact polar lipid with microbial community composition of vent deposits of the Rainbow and Lucky Strike hydrothermal fields

The intact polar lipid (IPL) composition of twelve hydrothermal vent deposits from the Rainbow (RHF) and Lucky Strike hydrothermal fields (LSHF) has been investigated in order to assess its utility as a proxy for microbial community composition associated with deep‐sea hydrothermal locations. Gene‐based culture‐independent surveys of the microbial populations of the same vent deposits have shown that microbial populations are different in the two locations and appear to be controlled by the geochemical and geological processes that drive hydrothermal circulation. Large differences in the IPL composition between these two sites are evident. In the ultramafic‐hosted RHF, mainly archaeal‐IPLs were identified, including those known to be produced by hyperthermophilic Euryarchaeota. More specifically, polyglycosyl derivatives of archaeol and macrocyclic archaeol indicate the presence of hyperthermophilic methanogenic archaea in the vent deposits, which are related to members of the Methanocaldococcaceae or Methanococcaceae. In contrast, bacterial IPLs dominate IPL distributions from LSHF, suggesting that bacteria are more predominant at LSHF than at RHF. Bacterial Diacyl glycerol (DAG) IPLs containing phosphocholine, phosphoethanolamine or phosphoglycerol head groups were identified at both vent fields. In some vent deposits from LSHF ornithine lipids and IPLs containing phosphoaminopentanetetrol head groups were also observed. By comparison with previously characterized bacterial communities at the sites, it is likely the DAG‐IPLs observed derive from Epsilon‐ and Gammaproteobacteria. Variation in the relative amounts of archaeal versus bacterial IPLs appears to indicate differences in the microbial community between vent sites. Overall, IPL distributions appear to be consistent with gene‐based surveys.     

Composition of the membranous deposits occurring in Gaucher's disease

We have isolated and purified low-density (1.08 g/ml) glucocerebroside-rich deposits from the spleen of a patient with Gaucher's disease. The organic phase obtained by chloroform-methanol (2:1) extraction of the deposits contains glucocerebroside, phospholipid, and free cholesterol in an approximate molar ratio of 12:3:2. The lipid-free residue accounting for approximately 12% of the dry weight of the deposits, contained protein and glycoprotein and accounts for the observation that the low-density deposits are significantly more dense than pure β-glucocerebroside (1.06 g/ml). The nonlipid residue contains galactose, hexosamine, and sialic acid and a PAS-staining glycoprotein with an approximate molecular weight of 95,000. This glycoprotein is extensively degraded by Pronase, but only when the structure of the deposits has been destroyed by organic solvent extraction. The nonlipid residue also contains several polypeptides with subunit molecular weights of 26,000–38,000.The deposits appear as a series of twisted bilayers, each 60 Å thick when prepared by freeze-etching methods. These bilayers are considered to be densely packed since staining methods visualize only the external surface.     

矿物油乳剂作用下橘小实蝇的产卵拒避及触角电位反应

为了研究矿物油乳剂对害虫行为的干扰作用,测定和比较了4种矿物油乳剂对橘小实蝇Bactrocera dorsalis (Hendel)的产卵拒避效果及在其作用下该虫的触角电位反应（EAG）,并测试了其中拒避效果最好的Caltex Lovis夏用油的不同施用方式（浸蘸法和喷雾法）及不同施用浓度（150,250,350,450倍液）对橘小实蝇产卵拒避的影响。结果显示：分别用4种矿物油乳剂200倍液以浸蘸法处理香蕉,仅Caltex Lovis夏用油处理对橘小实蝇产卵拒避效果显著,其平均产卵孔数仅为清水对照的15.14%;其他3种矿物油乳剂则没有明显效果。这表明矿物油乳剂对昆虫行为的干扰作用与其组成成分相关。4种矿物油乳剂对橘小实蝇的产卵拒避效果与各矿物油乳剂的50倍液滴于滤纸条后0.5 h的雌成虫EAG值间无显著相关性,但与滴于滤纸条后3 h（滤纸条上水分已蒸发）的EAG值间有显著的负相关性,说明矿物油乳剂的挥发性组分对橘小实蝇的产卵拒避影响不大,因此推测矿物油乳剂在植物表面形成的油膜对植物挥发性物质的封闭作用与其产卵拒避效果可能有一定的关系。浸蘸法不同浓度处理间的产卵拒避效果无显著差异,均明显高于喷雾法处理及清水对照。在喷雾法处理中,仅150倍液有显著产卵拒避效果。这说明,矿物油乳剂需要在植物表面达到一定的沉积量,才能对橘小实蝇有较好的产卵拒避作用。与喷雾法相比,浸蘸法可能较利于矿物油在植物表面的沉积,这也佐证了矿物油乳剂所形成油膜的封闭性与其产卵拒避效果有一定的关系。     

Ultrastructural and microanalytic study of gold depots in the synovial membrane of man and animals during treatment with sodium aurothiopropanol sulfonate

In inflammatory rheumatism treated by gold therapy synoviocytes A are stuffed with gold salt deposits leading to a therapeutic thesaurismosis. These deposits are localized in lysosomes, then called aurosomes. However they may be rarely near collagen fibers or free, particularly in ankylosing spondylitis synovitis. Their structural morphological aspect is the same in several human rheumatic diseases and in rabbit experimental arthritis whatever the gold salt used. In such deposits, microprobe analysis shows gold and sulphur. This latter is probably given by the cell. Therapeutic effect of gold salts may imply the effect of the thiol moiety and the gold metal one.