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781.
782.
Martha C. Hawes Laura Y. Smith Martha Stephenson 《Plant Cell, Tissue and Organ Culture》1991,27(3):303-308
Root border cells were isolated from alfalfa seedlings, and incubated in culture medium with growth regulators. Alfalfa seedlings yielded 1500±100 cells per root, and initial viability of the cells was 95±5%. Multiple cell divisions occurred in the border cells within two weeks. Cell clusters transferred to solidified medium containing growth regulators developed into rapidly growing, friable callus. When transferred to growth regulator-free medium, some of the calluses generated normal roots.Abbreviations BRD cells
border cells
- SHDN
Schenk & Hildebrandt salts medium with growth regulators
- SHO
Schenk & Hildebrandt salts medium without growth regulators
- NAA
I-naphthaleneacetic acid 相似文献
783.
The effect of dibutyryl cyclic AMP on the transport of α-methyl-d-glucoside and α-aminoisobutyric acid in separated tubules and purified brush border membranes from rabbit kidney was investigated using a rapid filtration procedure. Dibutyryl cyclic AMP stimulated the uptake of α-methyl-d-glucoside and α-aminoisobutyric acid by separated renal tubules in agreement with prior studies utilizing renal slices (Rea, C. and Segal, S. (1973) Biochim. Biophys. Acta 311, 615–624; Weiss, I.W., Morgan, K. and Phang, J.M. (1972) J. Biol. Chem. 247, 760–764). However, in contrast to previous reports, no preincubation of the tissue with dibutyryl cyclic AMP was required for stimulation of transport to be manifest. Dibutyryl cyclic AMP stimulated oxygen consumption by separated tubules suggesting that stimulation of transport may occur by a linkage with renal oxidative metabolism. Dibutyryl cyclic AMP increased the uptake of α-aminoisobutyric acid into purified renal brush border membranes. However the uptakes of α-methyl-d-glucoside, proline, leucine and phosphate into brush border membranes were significantly inhibited. 相似文献
784.
Robert D. Gunther Richard E. Schell Ernest M. Wright 《The Journal of membrane biology》1984,78(2):119-127
Summary The ion permeability of rabbit jejunal brush border membrane vesicles was studied by measuring unidirectional fluxes with radioactive tracers and bi-ionic diffusion potentials with the potential-sensitive fluorescent dye, diS–C3-(5). Tracer measurements provide estimates of the absolute magnitudes of permeability coefficients, while fluorescence measurements provide estimates of relative and absolute ion permeabilities. The magnitudes of the permeability coefficients for Na+, K+, Rb+, and Br– were approximately 5 nanoliters/(mg protein × sec) or 10–5 cm/sec as determined by radioactive tracer measurements. The apparent selectivity sequence, relative to Na+, as determined by bi-ionic potential measurements was: F–, isetheionate, gluconate, choline (<0.1)+(1.0)–(1.5)=NO
3
–
(1.5)
–(2.3)+(2.4)+(2.5)+(2.6)+(3.9) 4
–
+(12)–(40). The origin of this selectivity sequence and its relationship to the ion permeability of the brush border membrane in the intact epithelium are discussed. 相似文献
–(2.3)
785.
786.
787.
Larvae of the tobacco budworm,Heliothis virescens, are resistant to high levels of ingested 20-hydroxyecdysone which could cause potential inhibition to the development of
many other lepidopteran species. This resistance is attributed to the ability of the larvae to metabolize this molting hormone
to its 22-acyl ester forms. When tobacco budworm larvae were fed large quantities of 20-hydroxyecdyone, the hormonal metabolites
were found in gut and fat body tissues. When incubated with 20-hydroxyecdysone gut tissue converted 20-hydroxyecdysone into
its 22-acyl ester metabolites. Lumen site of the midgut was found to be the major location of this bio-transformation. In
contrast, fat body tissue failed to convert 20-hydroxyecdysone to 22-acyl ester metabolitesin vitro. After the oral injection of3H-ecdysone, the major metabolites formed were ecdysone 22-acyl esters whereas the majority of3H-ecdysone was transformed to polar metabolites after it was injected into the hemocoel of the larvae. Similar distributions
of ecdysteroid 22-O-acyltransferase and alkaline phosphatase activity in subcellular fractions demonstrates the co-localization of these enzymes
in plasma membrane of the gut epithelial cells. These results suggest that gut brush border membrane is the major site of
ecdysteroid 22-acyl ester formation inH. virescens larvae. 相似文献
788.
V K Antonov T I Vorotyntseva A G Bessmertnaya LYaMikhailova M I Zilberman 《FEBS letters》1984,171(2):227-232
The kinetics of uptake of radioactive label from [U-14C]Gly, L-[4,5-3H]Leu and the dipeptide [14C]Gly-L-[4,5-3H]Leu by the brush border membrane vesicles of porcine small intestine have been studied. The effect of aminopeptidase N inhibitors and leucine-binding protein on accumulation rates has also been tested. Comparison of the kinetic parameters for uptake and hydrolysis of Gly-L-Leu makes it possible to conclude that the dipeptide transfer includes two conjugated steps, viz., hydrolysis catalysed by aminopeptidase N and transport of the resultant free amino acids by a specific carrier. 相似文献
789.
Sarah Stewart Ali Jeewajee Thomas J. Wills Neil Burgess Colin Lever 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2014,369(1635)
The spatial mapping function of the hippocampal formation is likely derived from two sets of information: one based on the external environment and the other based on self-motion. Here, we further characterize ‘boundary vector cells’ (BVCs) in the rat subiculum, which code space relative to one type of cue in the external environment: boundaries. We find that the majority of cells with fields near the perimeter of a walled environment exhibit an additional firing field when an upright barrier is inserted into the walled environment in a manner predicted by the BVC model. We use this property of field repetition as a heuristic measure to define BVCs, and characterize their spatial and temporal properties. In further tests, we find that subicular BVCs typically treat drop edges similarly to walls, including exhibiting field repetition when additional drop-type boundaries are added to the testing environment. In other words, BVCs treat both kinds of edge as environmental boundaries, despite their dissimilar sensory properties. Finally, we also report the existence of ‘boundary-off cells’, a new class of boundary-coding cells. These cells fire everywhere except where a given BVC might fire. 相似文献
790.
Wolfram Nagel 《The Journal of membrane biology》1978,42(2):99-122
Summary The effect of ADH upon the intracellular potential and the resistance of inner and outer borders of the transport pathway was investigated on isolated skins ofRana temporaria. Within 40 min after ADH (100-300 mU/ml), the intracellular potential under short-circuit conditions decreased to about 40% of the control value (–79±4 mV), concomitant with an increase in the short-circuit current to about 160% of the control value. Amiloride, applied when steady values under ADH had been reached, caused an immediate rise of the intracellular potential to values typical for control conditions. This confirms (i) the intracellular location of the microelectrode and the absence of impalement artifacts, and (ii) the ineffectiveness of ADH upon the electromotive forces of the inner border. ADH had no effect upon the intracellular potential after blockage of the Na entry by Amiloride. The equilibrium potential of the outer border was estimated to be about +20 mV under the influence of ADH. As this value is considerably less positive than might be expected for the chemical potential of Na, a significant contribution of ions other than Na to the outer border conductance and equilibrium potential is implicated. The resistance of the outer border was more significantly decreased than that of the active transcellular pathway after ADH due to an increase in the inner border resistance, which exceeded that of the outer border after ADH. The effect of ADH upon the outer membrane characteristics would be underestimated by a factor of two, if the alterations of the electrical potential difference were not taken into consideration. 相似文献