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1.
Günter Kämper Hans-Ulrich Kleindienst 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1990,167(2):193-200
1. | Filiform hairs of various lengths on the cerci of adult crickets vibrate in a sound field. These movements were measured with a photodetector for sound frequencies from 10 Hz to 200 Hz in the species Acheta domestica, Gryllus bimaculatus and Phaeophilacris spectrum. |
2. | With low air-particle velocities, the hair shafts were deflected sinusoidally from their resting position, without bending or secondary oscillations (Figs. 2 A, 3 A). At higher velocities (from ca. 80 mm/s peak velocity, depending on the properties of the individual hairs), the shaft struck the cuticular rim of the socket in which the base of the hair is seated (Fig. 2B). This contact was made at an average angular displacement from the resting position of 5.16°±1.0°. |
3. | The best frequencies of the hairs were found to be between 40 Hz and 100 Hz (Fig. 5A). The slope of the amplitude curve for constant peak air-particle velocity at frequencies below the best frequencies was between 0 and 6 dB/octave. Long hairs had smaller slope values than short hairs (Fig. 5C). |
4. | At its best frequency the ratio of maximal tip displacement of a hair to the displacement of the air particles in the sound field was between 0.2 and 2. Only a small number of hairs (2 out of 36) showed tip displacements exceeding twice the air-particle displacement. The values of maximal angular displacement were not correlated to hair length (Fig. 5 B). |
5. | The angular displacement of the hairs was phase shifted with respect to the air-particle velocity by 0° to +45° (phase lead) at sound frequencies around 10 Hz and by -45° to -120° (phase lag) at 200 Hz (Figs. 3C, 4B). At a particular frequency long hairs tended to have larger phase lags than shorter hairs (Fig. 5D). |
2.
Dynamics of the cytoskeleton in Amoeba proteus 总被引:3,自引:0,他引:3
Fluorescein-labeled muscle actin was microinjected into Amoeba proteus and followed during intracellular redistribution by means of the image-intensification technique. The fully polymerization-competent protein becomes part of the endogenous actomyosin system undergoing dynamic changes over time periods of several hours. Single-frame analysis of long-term sequences enabled the direct demonstration of both the contractile activities and morphological transformations of microfilaments in normally locomoting, immobilized and phagocytozing specimens. In normally locomoting cells the filament layer undergoes continuous changes in spatial distribution depending on the actual pattern of cytoplasmic streaming and cell shape. The highest degree of differentiation is always maintained in the intermediate region between the front and the uroid, thus indicating this segment of the cortex to be the most important site in generating motive force for pseudopodium formation and ameboid movement. In immobilized cells contracted by the application of ruthenium red or relaxed by different anesthetics, the filament layer forms a continuous thick sheath beneath the cell surface or becomes completely disintegrated. In phagocytozing cells the local polymerization of actin at the tip of pseudopodia forming the food-cup and around the nascent phagosome points to a significant participation of the actomyosin system in the process of capturing and constricting prey organisms. Although our results provide clear evidence for the overall importance of motive force generation according to the hydraulic pressure theory, some motile phenomena exist in Amoeba proteus that cannot exclusively be explained by this mechanism. 相似文献
3.
Dr. Hans-Ulrich Schnitzler 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1970,68(1):25-38
Zusammenfassung
Chilonycteris rubiginosa erzeugt in allen Orientierungsituationen dreiteilige Ortungslaute. Im Anfangsteil steigt die Frequenz um etwa 1–2 kHz an. Der folgende Mittelteil hat eine konstante Frequenz von etwa 57 bis 57,6 kHz. Im Endteil fällt die Frequenz um etwa 8 kHz ab. Die Laute werden in Folgen von Lautgruppen ausgesendet.CR erzeugt pro Flügelschlag eine Lautgruppe. Im freien Flug zeigt CR Gruppen mit 2 Lauten von etwa 17–23 msec Dauer. Landende Fledermäuse senden in der Annäherungsphase Gruppen mit einer zunehmenden Zahl immer kürzerer Laute und in der Schlußphase eine längere Gruppe mit vielen kurzen Lauten.Fliegende Tiere senken die Frequenz des konstantfrequenten Mittelteils immer um etwa den Betrag der durch die Fluggeschwindigkeit bedingten Dopplereffekte ab, so daß die von den Tieren gehörte Echofrequenz nahezu konstant in Höhe der vor dem Flug ausgesendeten Frequenz gehalten wird.CR zeigt Kopf- und Ohrbewegungen. Die Ohrbewegungen stehen in Beziehung zur Lautaussendung.
Echolocation by the bat Chilonycteris rubiginosa
Summary Chilonycteris rubiginosa (CR) produces tripartite ultrasonic sounds in all orientation situations. During the first part the frequency rises by 1–2 kHz. The following middle part has a constant frequency of about 57–57,6 kHz. In the terminal part the frequency decreases by about 8 kHz. The sounds are emitted as a sequence of groups of sounds.In flight they produce per wingbeat one group of sounds at a repetition rate of 10–11 Hz. In free flight CR emits groups of 2 sounds of about 17–23 msec duration. During the approach landing bats emit groups consisting of an increasing number of sounds of decreasing duration. During the terminal phase the group is longer in duration and consists of many short sounds.Flying CR lower the frequency of the middle part by an amount which compensates for Doppler shifts caused by the flight velocity. The frequency heard by the bats is, thus, always kept constant and equal to a frequency which is about 100–150 Hz above the medium frequency emitted before the flight. CR shows head and ear movements. The ear movements are correlated to the sound emission.相似文献
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Immature zygotic embryos from spring barley cv. Dissa were used to induce somatic embryogenenesis. Up to 158 germinated somatic embryos could be recovered per plated zygotic embryo. Critical factors for obtaining a high yield of regenerants were the size of the explant, the level of 2,4-D used for callus induction and the careful division of callus at each subculture. Use of microsections of immature embryos as explants revealed a pronounced gradient of callus formation and embryogenic response across the scutellum. Sections from the scutellar tissue at the coleoptilar end of the embryo gave the most callus and were highly embryogenic. The regeneration response of sectioned explants was comparable to that recovered from intact embryos of similar size. 相似文献
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8.
Hans-Ulrich Meisch Helga Benzschawel Hans-Joachim Bielig 《Archives of microbiology》1977,114(1):67-70
Cells of Chlorella pyrenoidosa, derived from vanadium free agar slants, respond with great sensitivity to microamounts of vanadium, added as NH4VO3 to autotrophic liquid cultures. Between 0.01 and 1 g V per litre nutrient medium (2·10-10-2·10-8g-at/l), the algae respond with a continuous increase in dry weight. At higher V-concentrations, further enhancement in biomass is accompanied by a additional increase in chlorophyll content. Maximum V-effect on both parameters was found to be at 500g V/l (10-5 g-at/l). Dry weight as well as chlorophyll content of Chlorella are decreased by concentrations above 25 mg V/l; 100 mg V/l (2·10-3 g-at/l) stop growth and cause death of the cells. The toxic threshold for the V-content in the algae was determined to be at 150–200 g V/g (3–4·10-6 g-at/g) dry weight.Two different pH-optima for a positive vanadium action on dry weight and chlorophyll biosynthesis were established, the first at pH 7, the other in the range pH 7.5–8. Two sites of vanadium action in green algae are discussed.Part I: Arch. Microbiol. 105, 77–82 (1975) 相似文献
9.
Hammes F Broger T Weilenmann HU Vital M Helbing J Bosshart U Huber P Odermatt RP Sonnleitner B 《Cytometry. Part A》2012,81(6):508-516
Accurate and sensitive online detection tools would benefit both fundamental research and practical applications in aquatic microbiology. Here, we describe the development and testing of an online flow cytometer (FCM), with a specific use foreseen in the field of drinking water microbiology. The system incorporated fully automated sampling and fluorescent labeling of bacterial nucleic acids with analysis at 5-min intervals for periods in excess of 24 h. The laboratory scale testing showed sensitive detection (< 5% error) of bacteria over a broad concentration range (1 × 10(3) -1 × 10(6) cells mL(-1) ) and particularly the ability to track both gradual changes and dramatic events in water samples. The system was tested with bacterial pure cultures as well as indigenous microbial communities from natural water samples. Moreover, we demonstrated the possibility of using either a single fluorescent dye (e.g., SYBR Green I) or a combination of two dyes (SYBR Green I and Propidium Iodide), thus broadening the application possibilities of the system. The online FCM approach described herein has considerable potential for routine and continuous monitoring of drinking water, optimization of specific drinking water processes such as biofiltration or disinfection, as well as aquatic microbiology research in general. 相似文献
10.
Kühn-Wache K Bär JW Hoffmann T Wolf R Rahfeld JU Demuth HU 《Biological chemistry》2011,392(3):223-231
Dipeptidyl peptidase 4/CD26 (DP4) is a multifunctional serine protease liberating dipeptide from the N-terminus of (oligo)peptides which can modulate the activity of these peptides. The enzyme is involved in physiological processes such as blood glucose homeostasis and immune response. DP4 substrate specificity is characterized in detail using synthetic dipeptide derivatives. The specificity constant k(cat)/K(m) strongly depends on the amino acid in P?-position for proline, alanine, glycine and serine with 5.0 x 10? M?1 s?1, 1.8 x 10? M?1 s?1, 3.6 x 102 M?1 s?1, 1.1 x 102 M?1 s?1, respectively. By contrast, kinetic investigation of larger peptide substrates yields a different pattern. The specific activity of DP4 for neuropeptide Y (NPY) cleavage comprising a proline in P?-position is the same range as the k(cat)/K(m) values of NPY derivatives containing alanine or serine in P?-position with 4 x 10? M?1 s?1, 9.5 x 10? M?1 s?1 and 2.1 x 10? M?1 s?1, respectively. The proposed existence of an additional binding region outside the catalytic center is supported by measurements of peptide substrates with extended chain length. This 'secondary' binding site interaction depends on the amino acid sequence in P?'-P?'-position. Interactions with this binding site could be specifically blocked for substrates of the GRF/glucagon peptide family. By contrast, substrates not belonging to this peptide family and dipeptide derivative substrates that only bind to the catalytic center of DP4 were not inhibited. This more selective inhibition approach allows, for the first time, to distinguish between substrate families by substrate-discriminating inhibitors. 相似文献