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1.
Larry J. Tilley 《Hydrobiologia》1989,174(2):133-149
Simultaneous hourly net collections in a meadow and canyon reach of a mountain stream determined diel and spatial abundances
of drifting Chironomidae larvae. Sixty-one taxa were identified to the lowest practical level, 52 in the meadow and 41 in
the canyon. Orthocladiinae was the most abundant subfamily with 32 taxa and a 24 h mean density of 294 individuals 100 m−3 (meadow) and 26 taxa and a mean of 648 individuals 100 m−3 (canyon). Chironominae was the second most abundant subfamily. Nonchironomid invertebrates at both sites and total Chironomidae
larvae (meadow) were predominantly night-drifting.
Parakiefferiella and Psectrocladius were day-drifting (meadow) whereas 8 other chironomid taxa (meadow) and 2 taxa (canyon) were night-drifting. All others were
aperiodic or too rare to test periodicity, Stempellinella cf brevis Edwards exhibited catastrophic drift in the canyon only. The different drift patterns between sites is attributed to greater
loss of streambed habitat in the canyon compared to the meadow as streamflow decreased. Consequent crowding of chironomid
larvae in the canyon caused catastrophic drift or interfered with drift periodicty. This study adds to knowledge of Chironomidae
drift and shows influences on drift of hydrologic and geomorphic conditions. 相似文献
2.
A comparative study of the development of Eimeria nieschulzi in vitro under aerobic and reducing conditions 总被引:3,自引:0,他引:3
Sporozoites of the rat coccidian, Eimeria nieschulzi Dieben, 1924 (Apicomplexa: Eimeriidae), were inoculated onto monolayers of normal rat kidney (NRK) fibroblasts and cultured either under aerobic (5% CO2/95% air) or reducing (desiccator jars modified into candle jars) conditions in RPMI-1640 supplemented with 5% fetal bovine serum, sodium bicarbonate, and antibiotics. Under aerobic conditions, first-generation meronts were observed at 2 days postinoculation (DPI) and, except for individual third-generation meronts that were seen at 5 and 6 DPI, no further development was noted. Under reducing conditions, however, first-generation meronts observed at 2-5 DPI underwent additional development to form second-generation meronts (3-5 DPI), third-generation meronts (3-7 DPI), and a small number of fourth-generation meronts (5-8 DPI). Both second- and third-generation meronts were abnormal, exhibiting gigantism although the merozoites produced appeared normal. The gradual degeneration of cell monolayers under reducing conditions prevented further observations beyond 8 DPI. These results suggest that atmospheric conditions play an important role in the development of E. nieschulzi and maintenance of reducing conditions may be one key to achieving enhanced development of some species of coccidia in vitro. 相似文献
3.
ATP-dependent translocation of amino phospholipids across the human erythrocyte membrane 总被引:5,自引:0,他引:5
Trace amounts of radiolabeled phospholipids were inserted into the outer membrane leaflet of intact human erythrocytes, using a non-specific lipid transfer protein. Phosphatidylcholine, phosphatidylserine and phosphatidylethanolamine were transferred from the donor lipid vesicles to the membrane of the intact red cell with equal ease, whilst sphingomyelin was transferred 6-times less efficiently. The transbilayer mobility and equilibrium distribution of the labeled phospholipids were assessed by treatment of the intact cells with phospholipases. In fresh erythrocytes, the labeled amino phospholipids appeared to move rapidly towards the inner leaflet. The choline phospholipids, on the other hand, approached an equilibrium distribution which strongly favoured the outer leaflet. In ATP-depleted erythrocytes, the relocation of the amino phospholipids was markedly retarded. 相似文献
4.
Up to 50% of the actin in erythrocyte membranes can be solubilized at low ionic strength in a form capable of inhibiting DNAse I, in the presence of 0.4 mM ATP and 0.05 mM calcium. In the absence of calcium and ATP, actin is released but is apparently rapidly denatured. Solubilization of G-actin increases with temperature up to 37 degrees C. At higher temperatures, actin is released rapidly but quickly loses its ability to inhibit DNAse I. 相似文献
5.
A comparative study has been made of the ability of metal ions to catalyze the Lobry de Bruyn-Alberda van Ekenstein transformation. An analytical enzymic assay system, which is highly sensitive and selective, was developed to monitor the rates of isomerization of hexose and triose phosphates. The metal ions catalyze the isomerization of hexose phosphates by virtue of their Lewis acid character with the first transition series being most effective. The metal ions also appear to have no ability to direct the course of the reactions. Amino acids also catalyze the isomerization apparently by virtue of the free carboxylate anion. 相似文献
6.
Bruce C. Tilley Janise L. Meyertons Mary P. Lechevalier 《Journal of industrial microbiology & biotechnology》1990,5(5):329-332
Summary A previously undescribed cryptic phage was found associated withMicromonospora purpurea ATCC 15835. 相似文献
7.
Comparative development of Cryptosporidium parvum (Apicomplexa) in 11 continuous host cell lines 总被引:5,自引:0,他引:5
Abstract Using standardized media, incubation, and parasite inoculating procedures, we compared development of Crytosporidium parvum between Madin-Darby bovine kidney (MDBK) cells and 10 additional host cell lines available through the American Type Culture Collection. Parasite development was assessed by counting parasite numbers atop monlayers in 25 random oil fields 68 h post-infection using Nomarski interference-contrast optics. Results revealed that the human ileocecal adenocarcinoma (HCT-8) cell line supported nearly twice the number of parasite developmental stages than MDBK cells or any of the other host cell types. 相似文献
8.
Basolateral plasma membrane localization of ouabain-sensitive sodium transport sites in the secretory epithelium of the avian salt gland 下载免费PDF全文
The distribution of Na+ pump sites (Na+-K+-ATPase) in the secretory epithelium of the avian salt gland was demonstrated by freeze-dry autoradiographic analysis of [(3)H] ouabain binding sites. Kinetic studies indicated that near saturation of tissue binding sites occurred when slices of salt glands from salt-stressed ducks were exposed to 2.2 μM ouabain (containing 5 μCi/ml [(3)H]ouabain) for 90 min. Washing with label-free Ringer's solution for 90 min extracted only 10% of the inhibitor, an amount which corresponded to ouabain present in the tissue spaces labeled by [(14)C]insulin. Increasing the KCl concentration of the incubation medium reduced the rate of ouabain binding but not the maximal amount bound. In contrast to the low level of ouabain binding to salt glands of ducks maintained on a freshwater regimen, exposure to a salt water diet led to a more than threefold increase in binding within 9-11 days. This increase paralleled the similar increment in Na+-K+-ATPase activity described previously. [(3)H]ouabain binding sites were localized autoradiographically to the folded basolateral plasma membrane of the principal secretory cells. The luminal surfaces of these cells were unlabeled. Mitotically active peripheral cells were also unlabeled. The cell-specific pattern of [(3)H]ouabain binding to principal secretory cells and the membrane-specific localization of binding sites to the nonluminal surfaces of these cells were identical to the distribution of Na+-K+-ATPase as reflected by the cytochemical localization of ouabain-sensitive and K+-dependent nitrophenyl phosphatase activity. The relationship between the nonluminal localization of Na+-K+-ATPase and the possible role of the enzyme n NaCl secretion is considered in the light of physiological data on electrolyte transport in salt glands and other secretory epithelia. 相似文献
9.
10.
Defects in the human androgen receptor cause a spectrum of defects in male phenotypic sexual development associated with abnormalities in the receptor protein assayed in cultured fibroblasts and in broken cell assays. In some patients these abnormalities are associated with absent ligand binding, in other qualitative or quantitative abnormalities of ligand binding are present, and in some no abnormality of ligand binding is detected. Analysis of the androgen gene structure in such patients has permitted identification of the causative mutation in many families. Although results of these studies often reinforce concepts established by in vitro mutagenesis studies of other steroid receptors, some mutations have provided unusual insight into the structural organization of the androgen receptor molecule. 相似文献