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51.
Jisuo Jin 《Palaeontology》2003,46(5):885-902
Eocoelia akimiskii sp. nov. from the Lower Silurian (upper Telychian) Attawapiskat Formation of Akimiski Island, James Bay, Nunavut, is the first and oldest Eocoelia to be described from the Hudson Bay Basin, one of three largest inland basins of North America. The new species lacks dental plates, dental cavities, and marginal deflection or lip, which indicates a post-Aeronian form of the well-known Eocoelia lineage. In rib numbers, Eocoelia akimiskii falls between E. curtisi and E. sulcata , being closer to E. sulcata . In rib strength, however, the new species is more closely allied to E. curtisi . Although Eocoelia is currently assigned to the Rhynchonellida because of its lack of spiralia, several features (particularly the lack of a septalium, the presence of a unique notothyrial platform and cardinal process, and dense, free-hanging fibrous growth frills) of the genus and other leptocoeliids are distinctly atypical of the rhynchonellides. The new species occurs in an inter-reef, shelly packstone facies within the Attawapiskat Formation, which is characterized by coral-stromatoporoid reefs with abundant, diverse, reef-dwelling brachiopods and other shelly organisms. The close association of Eocoelia akimiskii with the Attawapiskat reefs supports a shallow subtidal (BA2) setting generally assigned to the Eocoelia Community. The reefs themselves, however, host an extremely abundant brachiopod fauna dominated by Pentameroides , Trimerella , Septatrypa , and Gypidula . Four species of Clorinda are also common elements of the reef-dwelling brachiopods. This demonstrates that the concept of the classic Early Silurian level-bottom brachiopod communities cannot be directly applied to reef-dwelling brachiopod communities. 相似文献
52.
Carbonized grains of sorghum, with consistent radiocarbon dates of ca. 8000 B.P., have been excavated at an early Holocene archaeological site (E-75-6) in Nabta Playa near the Egyptian-Sudanese border. The objective of the investigations reported here was to classify these early sorghum grains within the known wild or domesticated races or working groups of sorghum through the use of image-analysis procedures. Image-analysis is a non-destructive analytical method that can provide rapid, repeatable, and accurate measurements of ancient cereal grains. Measurements were taken on samples representing the five major domesticated sorghum races, eight wild relatives, and samples from the Nabta Playa and Jebel et Tomat excavation sites. Statistical and clustering techniques indicated significant differences existed among the sorghums with respect to the various measurements made. Sorghum from Nabta Playa was significantly smaller, with respect to most measurements, than either the wild relatives or the five cultivated sorghums. Smaller grain size and the lack of any spikelets containing attached branchlets of the inflorescence or rachis fragments suggest that the material harvested and eaten at the Nabta Playa site were of a wild type. 相似文献
53.
Evidence for plant exploitation and vegetation history from three Early Neolithic pre-pottery sites on the Euphrates (Syria) 总被引:3,自引:0,他引:3
George Willcox 《Vegetation History and Archaeobotany》1996,5(1-2):143-152
Archaeobotanical results based on a limited number of samples from three aceramic sites dating from 9800 to 7800 B.P., which
are under excavation in the valley of the Middle Euphrates, are discussed. The finds are presented simply by presence, and
are compared to the contemporary vegetation and finds from similar sites. Carbonised plant remains recovered by flotation
from levels dated to between 9800 and 9200 B.P. (Dja'de and Jerf al Ahmar) indicate that wild cereals (einkorn wheat, rye
and barley) and pulses (lentils, pea and bitter vetch) were exploited. Other plants such as wild grasses, Pistacia, wild almond and oak, suggest that the local vegetation provided a rich diversity of resources. A study of possible weed
taxa is being carried out in order to see whether this assemblage could be used to identify the cultivation of morphologically
wild cereals for this period. Ninth millennium B.P. levels at Halula see the appearance of domestic crops such as emmer, naked
wheat and barley, but wild-type cereals persist. The cultivars appear to have been introduced from elsewhere and later ninth
millennium B.P. species include olive and flax. Ash, vine, maple, plane, alder and elm from the gallery forest, wild rye,
wild einkorn, deciduous oak, wild almond, Pistacia, and Pyrus, from the hinterland, indicate cooler conditions. 相似文献
54.
Hermann Behling 《Vegetation History and Archaeobotany》1996,5(3):241-246
Palynological studies on late Quaternary lake sediments from the region of the Amazon estuary, 100 km north-east of Belém, Pará State, Brazil, enable reconstruction of lowland Amazonian rain forest during the Late-glacial and Holocene periods. Late-glacial forests included populations of Podocarpus which suggests a distinct climatic cooling. Ilex was abundant in the early Holocene. Records of the mangrove taxon, Rhizophora, indicate rapid Atlantic sea-level rise in the beginning of the Holocene. High charcoal representation may reflect the first arrival of Amerindians in the Amazon coastal area, probably about 10 800 B.P. 相似文献
55.
H. Ü. Kolukisaoglu S. Marx C. Wiegmann S. Hanelt H. A. W. Schneider-Poetsch 《Journal of molecular evolution》1995,41(3):329-337
Thirty-two partial phytochrome sequences from algae, mosses, ferns, gymnosperms, and angiosperms (11 of them newly released ones from our laboratory) were analyzed by distance and characterstate approaches (PHYLIP, TREECON, PAUP). In addition, 12 full-length sequences were analyzed. Despite low bootstrap values at individual internal nodes, the inferred trees (neighbor joining, Fitch, maximum parsimony) generally showed similar branching orders consistent with other molecular data. Lower plants formed two distinct groups. One basal group consisted of Selaginella, Equisetum, and mosses; the other consisted of a monophyletic cluster of frond-bearing pteridophytes. Psilotum was a member of the latter group and hence perhaps was not, as sometimes suggested, a close relative of the first vascular plants. The results further suggest that phytochrome gene duplication giving rise to a- and b- and later to c-types may have taken place within seedfern genomes. Distance matrices dated the separation of mono- and dicotyledons back to about 260 million years before the present (Myr b.p.) and the separation of Metasequoia and Picea to a fossil record-compatible value of 230 Myr B.P. The Ephedra sequence clustered with the c- or a-type and Metasequoia and Picea sequences clustered with the b-type lineage. The paleoherb Nymphaea branched off from the c-type lineage prior to the divergence of mono- and dicotyledons on the a- and b-type branches. Sequences of Piper (another paleoherb) created problems in that they branched off from different phytochrome lineages at nodes contradicting distance from the inferred trees' origin.
Correspondence to: H.A.W. Schneider-Poetsch 相似文献
56.
Fresh and dry body weights (FW, DW) were greater for adult southern green stink bug,Nezara viridula (L.) than for the brown stink bug,Euschistus heros F. throughout the year in southern Brazil. FemalesN. viridula significantly increased FW and DW in late summer-early autumn, and during mid-spring; femaleE. heros did not show the same rates of increase in FW and DW. FemaleN. viridula were heavier than males, particularly during summer; however, female and maleE. heros were generally similar in weight.E. heros contained significantly greater amounts of lipid thanN. viridula, during mid-autumn to early-spring (April–September). Survivorship (%) and total longevity ofE. heros adults provided water only was greater (34.6–24.6 days, for females and males) than that forN. viridula (14.8–13.0 days); without water and food, longevity was drastically reduced (<7 days) for both species. 相似文献
57.
Chaetoceros muelleri (Schütt) was cultured on a thermal gradient plate, subjected to two media types with a range of specific
conductances, and evaluated for growth and neutral lipid accumulation. Growth was measured directly by daily changes in cell
numbers and indirectly by changes in optical density at 750 nm. C. muelleri exhibited a growth rate of at least two doublings
day-1 over broad temperature (20 to 35 °C) and conductance ranges (10 to over 60 mS cm-1) and the optimum growth rate approached
4.0 doublings day-1 at 30 °C and a conductance of 25 mS cm-1. Intracellular neutral lipid storage was evaluated with fluorometry
and epifluorescent microscopy using the fluorochrome Nile Red. Gravimetric analysis revealed a total lipid content in nitrogen-depleted
cultures of C. muelleri of over 400 mg L-1, five to seven times that observed in nitrogen-replete cultures. Based on its high
growth rate, tolerance to a broad range of temperatures and specific conductances, and large quantity of intracellular lipid,
C. muelleri may have potential for exploitation as a renewable precursor to liquid fuels or as a lipid source.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
58.
BCL-2-Related Protein Expression in Apoptosis: Oxidative Stress Versus Serum Deprivation in PC12 Cells 总被引:5,自引:0,他引:5
Abstract: Expression of the BCL-2 protein family members, BAX, BAK, BAD, BCL-xL, BCL-xS, and BCL-2, was measured (by western blotting using specific antibodies) in PC12 cells before and during apoptosis induced by either H2 O2 treatment or by serum deprivation and during rescue from apoptosis by nerve growth factor (NGF). H2 O2 -induced apoptosis, as measured by DNA fragmentation, caused: (a) a dose-dependent increase in BAX, (b) a dose-independent increase in BAK, and (c) a dose-dependent inhibition of BAD expression. By comparison, apoptosis induced by serum deprivation resulted in a time-dependent decrease in both BAX and BAK, along with a dramatic and sudden decrease in BAD expression. However, when PC12 cells were incubated in an apoptosis-sparing medium (i.e., NGF-supplemented serum-free medium), both BAX and BAK were increased significantly, whereas BAD expression remained inhibited. BCL-xL expression was increased by H2 O2 but unaffected by serum deprivation or long-term NGF treatment. Neither BCL-2 nor BCL-xS expression could be detected in PC12 cells under the experimental conditions tested. Our results show that the expression of BAX, BAK, BAD, and BCL-xL is altered in a stimulus-dependent manner but cannot be used to define whether a cell will undergo or survive apoptosis. The similarity between changes in expression of BCL-2-related proteins induced by H2 O2 exposure and NGF rescue could reflect activation in part of a common antioxidant pathway. 相似文献
59.
60.
ochotonidaeThomas,l897AlloptoxDaw8on,l96lAlloptoxsihongensis8p.nov.(Figs.lAi6)HolotypeArightp3,V884o.7.Paratypesldp3,V884o.l;3p3,V884o.3,5,6;1p4,V884O.9;2ml/m2,V884o.l2,16;Afragmentof1eftmandiblewithp4,V884O.l8;thefrontpartofrightman-diblewithi2,p3-p4,V884o.24;2I2,V884O.21,23;4P3,V884O-31-33,56;P4,V884o.27;AfragmentofleftupperjawwithP3-M1,V884o-57;2M2,V884o.5o,53.TypelocalityS0nglinzhuang,Sih0ngC0unty,Jiangsu.StratumtypicumandageXiaca0wanFormation,.EarIyMi0cene(Shan-wangian),eq… 相似文献