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11.
Summary Bacterivory was detected by incorporation of 0.57 m diameter, fluorescent polystyrene beads and fluorescently labeled bacteria (FLB) in two cultured species of Cryptomonas (C. ovata and C. erosa), and a population of Cryptomonas sp in a humic, mesotrophic lake. Rates of ingestion and clearance were very low, and similar for the cultures and the in situ population. The in situ population incorporated 0.7–1.7 bacteria cell-1 h-1, thereby ingesting 0.3%–2.0% of the total bacterial numbers present in the water per day, and receiving less than 2% of its carbon content per day through bacterivory. Thus, bacterivory by Cryptomonas was quantitatively important neither as a sink for bacterial biomass, nor as a carbon source for the algal cells. Possibly, it served in the uptake of essential nutrients. 相似文献
12.
Response of grasshoppers (Orthoptera: Acrididae) to livestock grazing in southeastern Arizona: differences between seasons and subfamilies 总被引:3,自引:0,他引:3
Summary Grasshopper densities were compared between grazed and ungrazed semidesert grassland sites in southeastern Arizona. Bouteloua-dominated perennial grass cover was about 1.5 times greater on the livestock exclosure. Grasshoppers were 3.7 times more abundant on the protected area in the summers of 1983 and 1984, when dominant species were grass-feeding members of the subfamily Gomphocerinae. In fall 1984, grasshoppers were 3.8 times more common on the grazed site, when dominants were mainly herb-feeders in the subfamily Melanoplinae. These results indicate important seasonal and taxonomic differences in the responses of grasshoppers to the activities of vertebrate grazers. 相似文献
13.
Methanospirillum hungatei gave a positive chemotactic response to acetate. 相似文献
14.
Dawson K 《Bioethics》1988,2(1):1-14
A basic consideration in research on human embryos is the controversy about when the embryo acquires moral status. The author refutes the contention that segmentation is the determinant of moral status. She notes that segmentation, as a stage in embryonic development, does not coincide with the development of "irreversible individuality" upon which the segmentation argument depends. Dawson also finds a lack of clarity in the meaning of "individuality." These problems, she maintains, prevent segmentation from being morally important and render the proposed 14-day limit on embryo research unnecessary. Dawson concludes that to introduce a time restriction on embryo research is premature because it is based on an inadequate philosophical argument. 相似文献
15.
Karen Barsuhn S. Theodore Chester Jr. Dr. Jane A. Z. Leedle 《Current microbiology》1988,16(6):337-341
The effectiveness of a buffered sodium oleate solution was evaluated for detaching bacteria from ruminal digesta samples. A response surface derived from an octagonal design was used to determine the pH and concentration combination for maximum detachment of total and cellulolytic bacteria. The total number of bacteria detached increased up to 81% over control with treatment of a pH 8.8 and 1.5% sodium oleate solution. The recovery of cellulolytic bacteria was decreased to 35% of control with treatment of a pH 9.0 and 0.1% sodium oleate solution. Attempts to improve the recovery of viable bacteria exposed to sodium oleate solutions were unsuccessful. This response surface design identified an optimal pH and concentration that were consistent with existing information regarding detachment of total bacteria, and suggested that sodium oleate, at the concentrations tested, was toxic to the cellulolytic population of the rumen. 相似文献
16.
Hans Fricke Karen Hissmann Jürgen Schauer Olaf Reinicke Lutz Kasang Raphael Plante 《Environmental Biology of Fishes》1991,32(1-4):287-300
Synopsis In 1987 and 1989 coelacanths were observed for the first time in their natural habitat with the help of submersibles. Coelacanths were found between 150–253 m depth, their preferential depth seems to be around 200 m; the water temperature ranged between 16.5–22.8° C. During the day coelacanths aggregate in small non-aggressive groups in sheltered lava-caves. Caves might be a limiting factor for distribution. At night they leave the caves for hunting by drifting singly along the steep lava slopes. They migrate between different caves located within a large home range covering more than 8 km coastline. Coelacanths are site-attached, some for a period of at least 2 years. Our own observations and earlier catch records show that only the west coast of Grand Comoro is a suitable coelacanth habitat with more structural complexity and prey fish abundance than other coastlines of the island. From our survey we estimated a total coelacanth population off Grand Comoro to be 150–210 individuals; a saturated population would be 370–510 individuals. This small relict population seems to be stable. International protection of coelacanths against commercial interests is needed 相似文献
17.
18.
Evaluation of Diverse Antisera, Conjugates, and Support Media for Detecting Bradyrhizobium japonicum by Indirect Enzyme-Linked Immunosorbent Assay 总被引:5,自引:5,他引:0 下载免费PDF全文
We evaluated three antisera and four enzyme conjugates for the detection of Bradyrhizobium japonicum by an indirect enzyme-linked immunosorbent assay in microtiter plates. Nitrocellulose membrane sheets were then evaluated as an alternative support medium by using some combinations. Partially purified immunoglobulin G (IgG) or unpurified antisera to strain USDA 110 raised in rabbits, goats, or sheep was reacted in microtiter plates with alkaline phosphatase conjugated to protein A, goat anti-rabbit (GAR), sheep anti-rabbit (SAR), or rabbit anti-goat (RAG) IgG. Cultures or nodules containing homologous rhizobia were detected with equal sensitivity when protein A, GAR, or SAR was reacted with 5 μg of protein IgG per ml or a 1:800 titer of antisera from rabbits, but not goats or sheep. RAG reacted with IgG or antisera from goats or sheep. The detection limit was 2 × 105 rhizobia per well. Rhizobia were spotted on nitrocellulose sheets as an alternative support medium, followed by soaking in 5 μg of protein per ml as IgG and 1:4,000 dilutions of protein A or GAR conjugate. Rhizobia in serogroup 110 were detected with the dye combination Nitro Blue Tetrazolium-5-bromo-4-chloro-3-indolyl phosphate (NBT-BCIP), and rhizobia in serogroup 122 were detected with fast red-naphthol phosphate (FR-NP). At the conclusion of the 5-h assay, purple (NBT-BCIP) or red (FR-NP) spots were visible in positive reactions. The sensitivity of detection was about 1,000 rhizobial cells or 3 μg of nodules tissue. 相似文献
19.
Glycophorin A was phosphorylated using protein kinases and the new protein was investigated using31P NMR spectroscopy. Most of these ~30 moles of phosphate were found to be attached to Ser and Thr. Some of these phosphate residues appear to be affected by the carbohydrate residues present. The phosphorylated protein appears to be in a severe state of aggregation, with the degree of aggregationpH-dependent. 相似文献
20.
Microinjection of neurotensin (NT; 2 and 5 μg) into the substantia nigra zona compacta caused an increase in dopamine (DA) and DA metabolites in the rodent globus pallidus and striatum which persisted for at least 20 hours after peptide administration. Similar NT treatments given unilaterally into the nigra caused circling away from the injected side in amphetamine-pretreated rats, but were without effect when microinjected into saline-pretreated animals. Circling also occurred when the animals were given amphetamine 20 hours after intranigral NT administration. Contralateral rotation was observed with unilateral intranigral injections of gamma-hydroxybutyric acid (GHB; 400 μg) or with lower intranigral GHB doses (250 μg) in amphetamine-pretreated animals. The effects of GHB and NT differed in the manner in which the animals rotated as well as in the profile of DA and DA metabolite changes induced by these drugs. These studies indicated that: (1) dopaminergic functions of the globus pallidus are influenced, like the striatum, by manipulations of the substantia nigra; (2) NT and GHB likely act via different mechanisms to effect nigral dopamine-containing cells; and (3) NT was capable of inducing changes in dopamine neurons which had long term consequences. 相似文献