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971.
A simple, inexpensive method is described for dialysis of microliter amounts of aqueous samples against large volumes of solution with complete recovery of the fluid dialyzed. An example is given of application of the method to separation of [3H]inulin from a monosaccharide. 相似文献
972.
Valuable biological information can be obtained by monitoring the movement of organisms. However, the choice of monitoring
method becomes highly restricted when following small organisms (<100 mm), especially in aquatic ecosystems. Stable isotopes
are being increasingly used in this respect but rarely at the local spatial scale, i.e. 10–1000 s of metres. We sought to
identify movement of small fishes between a main river channel and its tributary. Little overlap in isotope baseline was detected
between the two channels despite some temporal variability in δ15N of baseline indicator organisms in the main river. The individuals of two small cyprinid fish species (Leuciscus souffia and Alburnoides bipunctatus) of all the size classes (40–100 mm) caught within the tributary showed considerable heterogeneity in δ15N values. Classification and discriminant analysis on isotope-derived data distinguished two significantly different groups.
Moreover, this result was supported by further sampling of fish caught in the main river (in May and December 2006). Alternative
hypotheses, such as dietary differences, biological factors, temporal shifts and spatial differences in diet, did not explain
δ15N variability. This application of stable isotopes at a relatively small spatial and temporal scales further demonstrates
its potential as a tool for ecologists. 相似文献
973.
Intracellular transport of cholesterol to the plasma membrane 总被引:10,自引:0,他引:10
We have modified a plasma membrane isolation procedure which utilizes DEAE-Sephadex beads (Gotlib, L. J., and Searls, D. B. (1980) Biochim. Biophys. Acta 602, 207-212) to rapidly measure intracellular transport of cholesterol from the site of synthesis in the endoplasmic reticulum to the plasma membrane. This transport process is rapid, with a half-time of about 10 min, has different kinetics from that of intracellular glycoprotein transport, and appears to be energy-dependent. 相似文献
974.
The effects of various anionic phospholipids on the in vitro assembly of MAP2/tubulin microtubules has been examined. We show that the potency to inhibit is related to the polarity of the phospholipids and that this is consistent with a mode of action involving the sequencing of microtubule-associated proteins (MAPs) by nonspecific electrostatic interactions. The inhibitory potency of phosphatidylinositol (PI) is, however, considerably larger than predicted by this model. The effects of PI on MAP2/tubulin microtubule assembly have therefore been examined in greater detail by preparing phosphatidylcholine (PC) liposomes doped with increasing amounts of PI. We show that when the PI is sufficiently dispersed by dilution with PC, it inhibits microtubule assembly by binding to MAP2 with an apparent stoichiometry, after correction for the bilamellar nature of the liposomes, of 1:1 mol.mol-1 PI:MAP2. Furthermore, we show that the Kd of this interaction is in the submicromolar range. 相似文献
975.
D I Medvedev I I Babichenko I Z Eremina A I Kravtsova 《Biulleten' eksperimental'no? biologii i meditsiny》1985,100(12):751-754
Electron microscopy of mouse neocortex was carried out during rehabilitation following long-term protein-caloric deficiency. Food rehabilitation led to partial recovery of brain ultrastructure, however, a high neuronal level of secondary lysosoms and lipofuscin bodies was preserved, with the changes in the spine apparatus and synaptic contacts persisting in neuropile. Carnitine addition to food during rehabilitation increased the number of free ribosomes in cortical neurons. A substantial development of granular endoplasmic reticulum was observed. A greater number of spine apparatus cisterns was detected, however, like in conventional rehabilitation, the width of synaptic clefts and postsynaptic densities remained narrower than in control mice. 相似文献
976.
Mononuclear phagocytes release interleukin-1 (IL-1), a 17-kDa polypeptide with diverse biological activities. IL-1 is synthesized as a precursor (31 kDa) which lacks a signal sequence or hydrophobic domains that could facilitate transmembrane translocation. Possible postsynthetic modifications of IL-1 that might account for its cellular transport were examined. We found that lipopolysaccharide stimulated, but not unstimulated, murine macrophages incorporated 32PO4 into the IL-1 alpha precursor (31 kDa) predominantly at residue serine 90. Released IL-1 alpha (17 kDa) is not phosphorylated in agreement with peptide sequence data that the site of 32P incorporation is in the amino-terminal one-third of the precursor. Approximately 10% of the phosphorylated IL-1 alpha precursor is membrane bound and associated with a fraction enriched in lysosomal vesicles. Together these data suggest mechanisms by which the postsynthetic proteolysis of the IL-1 alpha precursor may be modified and cellular transport of IL-1 alpha is accomplished. 相似文献
977.
This study has demonstrated that aneurysms occur in about 50 percent of the rat femoral arteries subjected to microvascular anastomosis. These aneurysms are consistent histologically--being characterized by medial necrosis, loss of elastic lamellae, and subintimal hyperplasia. Mechanical trauma is implicated as a factor in their pathogenesis, though further study in necessary to define the exact etiology. 相似文献
978.
979.
The immunological network at the site of tumor rejection 总被引:4,自引:0,他引:4
R Evans 《Biochimica et biophysica acta》1986,865(1):1-11
The tumor mass irrespective of its type or location in the body has long been shrouded in mystery and even today we still have only a tentative handle on its secrets. Attempts to manipulate either the tumor cells per se or host-derived leukocytes have, on the whole, not been successful or at best questionable. The ability of the host to respond immunologically to TSTA is well documented, yet again attempts to manipulate this response have been disappointing. One of the problems has been a lack of knowledge concerning the tumor mass and its constituents, such as the intratumor leukocytes, and the significance of their presence to the biological properties of the neoplasm [8,9,80]. The purpose in studying the immunological network is, in part, to try to assign a function to these cells on the premise that lymphoid elements and macrophages have a potential role to play in recognition of TSTA. The advantage of adoptive immunotherapy model systems is that tumor rejection can be achieved under controlled conditions and this allows an analysis of the immunological network and its individual circuits. At the same time, valuable information on the mechanisms of action during adoptive immunotherapy and how best to improve therapeutic protocols is acquired. 相似文献
980.
C F Nassar E W Khairallah M G Nasser Z M Habbal 《Comparative biochemistry and physiology. A, Comparative physiology》1988,89(2):197-201
1. The effect of colchicine, cytochalasin-B and procaine on calcium transport across the rat small intestine was investigated. The results obtained show the following: 2. Colchicine and cytochalasin-B at different concentrations inhibited significantly (P less than 0.001) calcium accumulation in rat intestinal cells, whereas procaine at different concentrations increased significantly (P less than 0.001) calcium accumulation in the rat small intestine. 3. Unidirectional influx of calcium across the rat small intestine was significantly inhibited (P less than 0.01) in the presence of colchicine and cytochalasin-B in the preincubation medium. Procaine, on the other hand, caused a significant increase (P less than 0.01) in the unidirectional influx of calcium across the rat intestinal cells. 4. The cell water content was not altered in the presence of the different drugs indicating that the changes in calcium transport across the rat intestinal cells are not due to alterations in the structure of the cell membrane. 相似文献