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41.
Andreas Elepfandt 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1986,158(2):235-238
Summary The ability of adultXenopus laevis to identify water wave frequencies was demonstrated by go/no-go conditioning. The acuity of frequency recognition is of absolute-pitch quality.Abbreviations
S+
stimulus with response reward
-
S-
stimulus with response punishment
-
u
discrimination index 相似文献
42.
The structural polarity of statocytes of Lepidium sativum L. is converted to a physical stratification by a root-tip-directed centrifugal acceleration. Sedimentation of amyloplasts and nucleus to the centrifugal (distal) cell pole and the lateral displacement of the distal endoplasmic reticulum (ER) complex occur after centrifugation for 20 min at an acceleration of 50 g. With higher doses (20 min, 100-2,000 g), smaller organelles become increasingly displaced. From the centrifugal to the centripetal cell pole, the following stratification is observed: 1) amyloplasts with mitochondria; 2) nucleus with mitochondria and a few dictyosomes, as well as laterally located ER; 3) dictyosomes with a few mitochondria; 4) vacuoles; and 5) lipid droplets. Within the first 7.5 min, after the roots have been returned to 1 g, the original arrangement of the amyloplasts sedimented on the underlying ER complex is reestablished in 66% of the statocytes. When roots previously centrifuged in an apical direction are exposed in a horizontal position to 1 g, the latent period of the graviresponse is increased by 7.5 min relative to the non-centrifuged controls. The kinetics of the response are identical to the controls. Roots centrifuged first in an apical direction and then for 2 h in a lateral direction (1,000 g) have statocytes with a physical stratification perpendicular to the root axis. A gravitropic curvature does not take place during the lateral centrifugation. These results support the hypothesis that the distal ER complex is necessary and sufficient for graviperception. 相似文献
43.
44.
45.
Andreas Schmid Gerhard Burckhardt Heinz Gögelein 《The Journal of membrane biology》1989,111(3):265-275
Summary Endocytotic vesicles from rat kidney cortex, isolated by differential centrifugation and enriched on a Percoll gradient, contain both an electrogenic H+ translocation system and a conductive chloride pathway. Using the dehydration/rehydration method, we fused vesicles of enriched endosomal vesicle preparations and thereby made them accessible to the patch-clamp technique. In the fused vesicles, we observed Cl– channels with a single-channel conductance of 73±2 pS in symmetrical 140mm KCl solution (n=25). The current-voltage relationship was linear in the range of –60 to +80 mV, but channel kinetic properties dependended on the clamp potential. At positive potentials, two sublevels of conductance were discernible and the mean open time of the channel was 10–15 msec. At negative voltages, only one substate could be resolved and the mean open time decreased to 2–6 msec. Clamp voltages more negative than –50 mV caused reversible channel inactivation. The channel was selective for anions over cations. Ion substitution experiments revealed an anion permeability sequence of Cl–=Br–=I–>SO
4
2–
F–. Gluconate, methanesulfonate and cyclamate were impermeable. The anion channel blockers 4,4-diisothiocyanatostilbene-2,2-disulfonic acid (DIDS, 1.0mm) and 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB, 0.1mm) totally inhibited channel activity. Comparisons with data obtained from radiolabeled Cl–-flux measurements and studies on the H+ pump activity in endocytotic vesicle suspensions suggest that the channel described here is involved in maintenance of electroneutrality during ATP-driven H+ uptake into the endosomes. 相似文献
46.
Creatine Transport in Cultured Cells of Rat and Mouse Brain 总被引:7,自引:3,他引:4
Astroglia-rich cultures derived from brains of newborn rats or mice use a transport system for the uptake of creatine. The uptake system is saturable, Na+-dependent, and highly specific for creatine and Na+. Kinetic studies on rat cells revealed a Km value for creatine of 45 microM, a Vmax of 17 nmol x h-1 x (mg of protein)-1, and a Km value of 55 mM for Na+. The carrier is competitively inhibited by guanidinopropionate (Ki = 15 microM). No such transport system was found in neuron-rich primary cultures from embryonic rat brain. It is hypothesized that creatine transport is an astroglial rather than a neuronal function. 相似文献
47.
48.
Andreas Pries Alexander Steinbüchel Hans G. Schlegel 《Applied microbiology and biotechnology》1990,33(4):410-417
Summary Transposon Tn 951-encoded -galactosidase was expressed in Pseudomonas saccharophila and enabled this bacterium to grow on lactose as sole carbon source. In contrast, -galactosidase was not expressed in Alcaligenes eutrophus even if the lacZ gene of Tn 951 was separated from the lacI gene. However, -galactosidase was expressed in A. eutrophus, if a DNA fragment, which was suspected to harbour the promoter of the A. eutrophus poly(3-hydroxybutyric acid)-synthetic genes, was ligated to the promoter probe vector pMC1403, which employs lac Z, Y as reporter genes. Plasmid pPL76, which harboured one of the promoter-lac fusions, enabled A. eutrophus not only to express -galactosidase but also to grow slowly on lactose (doubling time = 25–30 h). Subsequently, the promoter-lac fusion was ligated to Tn5 in pSUP5011 and was inserted into the genome of A. eutrophus H16 and of the glucose-utilizing mutant H16-G+1 by applying the suicide plasmid technique. Two recombinant strains, H16-cPL and H16-G+1-cPL, which grow with a doubling time of 16–23 h on lactose, were investigated in detail. The cells only utilized the glucose residue of lactose as a carbon source for grouth and excreted galactose into the medium. Only after the Escherichia coli gal operon had been cloned in vector pVK101 and had been mobilized to H16-cPL or H16-G+1-cPL, was lactose completely utilized; no galactose was detected in the medium and the growth yields increased twofold. Depending on the orientation of the gal operon in pVK101, the expression of galactokinase seems to be dependent either on the promoter of aminoglycoside phosphotransferase gene (kan) or on the promoter of the tetR gene.
Offprint requests to: A. Steinbüchel 相似文献
49.
Kirstin Schultze Klaus Janke Andreas Krüß Wolfgang Weidemann 《Helgoland Marine Research》1990,44(1):39-51
This paper describes the macroflora and macrofauna associated with two bull kelp species,Laminaria hyperborea andL. digitata, at the island of Helgoland, North Sea. During a study period of seven months (March–September 1987), 29 macroflora species
and 125 macrofauna species were found. The dominant taxonomic groups were Polychaeta (25 species), Bryozoa (17), Amphipoda
(14), Hydrozoa (10) and Ascidiae (8). The species maximum was in July. In general,L. hyperborea was preferred as a substrate for settlement toL. digitata. Composition of the communities associated with kelp changed during the season according to exposure to wave action, and
according to location on the kelp thallus. The rhizoid community of both kelps bore more species at exposed locations. Wave-exposedL. digitata lacked obvious faunal settlement on both phylloid and cauloid. Phylloid and cauloid ofL. hyperborea were chosen as an attractive substrate at both sheltered and wave-exposed locations, showing an association of encrusting
bryozoan and hydrozoan colonies. 相似文献
50.
Andreas Schmidt-Rhaesa 《Zoomorphology》1996,116(3):133-142
The nervous system of Nectonema munida is shown to be composed of a brain, a ventral nerve cord with an anterior and a posterior enlargement, a dorsal nerve cord
and a plexus-like basiepidermal nervous system. The ultrastructure of these parts is given. Additionally, the ventral nerve
cord of Gordius aquaticus is ultrastructurally described. The results are compared with the literature to work out the ground pattern of the Nematomorpha
according to the nervous system. This contains a circumpharyngeal brain with a main subpharyngeal portion and a weak suprapharyngeal
portion, a ventral and dorsal intraepidermal nerve cord and a peripheral nervous system. The ground pattern of the nervous
system of Nematomorpha is then compared to that of other Nemathelminthes. The form of the brain and the distribution of perikarya
are derived characters of the Nematomorpha. The existence of an unpaired ventral and an unpaired dorsal nerve cord and the
position of these two cords in epidermal cords are synapomorphies of the Nematomorpha and the Nematoda.
Accepted: 7 July 1996 相似文献