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1.
Hansjürgen Dahmen 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1991,169(5):623-632
The angular distribution of the optical axes of the ommatidia in the eyes of waterstriders (Gerris lacustris) has been investigated using antidromic illumination.
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1. | Each eye contains about 920 ommatidia arranged in approximately 40 nearly horizontal rows (Figs. 5, 6). |
2. | There is an acute zone (visual streak) of ±5° around the eye equator with high vertical resolution (Fig. 9). |
3. | The horizontal interommatidial angle oh varies little with altitude and is in the frontal parts of the eye equal to the (horizontal) interrhabdomere angle rh (Fig. 10). |
4. | Above and below the visual streak the eye is adapted to the perception of relative height or depth constancy (Fig. 13). |
5. | Reconstruction of the viewing directions of the rhabdomeres in the visual streak reveals that characteristic groups of rhabdomeres in different ommatidia coincide in their receptive fields. Optical prerequisites for two types of neural superposition can be found: one of medium neural summation but highest sampling frequency, the other of highest neural summation at the cost of resolution (Fig. 11). |
6. | The correspondence of the limits of resolution due to diffraction and finite sampling frequency is discussed. |
2.
Water uptake and transport in lianas and co-occurring trees of a seasonally dry tropical forest 总被引:5,自引:0,他引:5
José Luis Andrade Frederick C. Meinzer Guillermo Goldstein Stefan A. Schnitzer 《Trees - Structure and Function》2005,19(3):282-289
Water uptake and transport were studied in eight liana species in a seasonally dry tropical forest on Barro Colorado Island, Panama. Stable hydrogen isotope composition (D) of xylem and soil water, soil volumetric water content (v), and basal sap flow were measured during the 1997 and 1998 dry seasons. Sap flow of several neighboring trees was measured to assess differences between lianas and trees in magnitudes and patterns of daily sap flow. Little seasonal change in v was observed at 90–120 cm depth in both years. Mean soil water D during the dry season was –19 at 0–30 cm, –34 at 30–60 cm, and –50 at 90–120 cm. Average values of xylem D among the liana species ranged from –28 to –44 during the middle of the dry season, suggesting that water uptake was restricted to intermediate soil layers (30–60 cm). By the end of the dry season, all species exhibited more negative xylem D values (–41 to –62), suggesting that they shifted to deeper water sources. Maximum sap flux density in co-occurring lianas and trees were comparable at similar stem diameter (DBH). Furthermore, lianas and trees conformed to the same linear relationship between daily sap flow and DBH. Our observations that lianas tap shallow sources of soil water at the beginning of the dry season and that sap flow is similar in lianas and trees of equivalent stem diameter do not support the common assumptions that lianas rely primarily on deep soil water and that they have higher rates of sap flow than co-occurring trees of similar stem size. 相似文献
3.
B. Dujon M. Bolotin-Fukuhara D. Coen J. Deutsch P. Netter P. P. Slonimski L. Weill 《Molecular & general genetics : MGG》1976,143(2):131-165
1. | A series of CS revertants has been selected from various strains (both + and –) carrying a CR mitochondrial mutation at the RIB1 locus. The properties of mitochondrial recombination exhibited by these CS revertants in various crosses, have been examined systematically. The allele of the CS revertants has been defined in crosses with + and – tester strains using two criteria: the polarity of recombination and a new criterium called relative output coefficient. We found that mutations of appear frequently associated with the mutations at the RIB1 locus selected from – strains but not with those selected from + strains. A new allelic form of (n) which had not been found amongst wild type yeast strains is characterised. Similarly n mutation was found frequently associated with CR mutants at the RIB1 locus selected from – CS strains but not with those selected from + CS strains. The n mutants, and the + and – strains, explain the groups of polarity previously observed by Coen et al. (1970). |
2. | Main features of mitochondrial crosses with n strains (+×n, –×n and n×n) are analysed. Recombination is possible between the different mitochondrial genetic markers. No high polarity of recombination is observed and the frequency of recombinants are similar to those found in homosexual crosses (+×+ and –×–). A striking property, observed for the first time, exists in crosses between + +×n CS strains and some – CREO mutants: the – CREO are unable to integrate by recombination their CR allele into the + mit-DNA of – CS strains while being capable of integrating it into + CS or – CS genomes. |
3. | It is proposed that the locus is the site of initiation of non reciprocal recombination events, the +/– pairing specifically initiates the non-reciprocal act while +/n or –/n pairings do not. |
4. | The molecular nature of the n mutation and its bearing on the structure of the locus are discussed. It is suggested that n mutations correspond to macrolesions (probably deletions) of a segment of the mit-DNA covering the and RIB1 loci. If n is a partial deletion of the – sequence the + could be an additionnal deletion of the n sequence. |
5. | The occurrence of spontaneous CR and ER mitochondrial mutations has been analysed by the Luria and Delbrück fluctuation test in – and n isonuclear strains. Results of these tests indicate that an intracellular selection of resistant copies preexisting the action of the antibiotic occurs. |
4.
Joachim Prager 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1976,110(1):33-50
1. | Action potentials of the mesothoracic tympanic organ's two receptor units (Al and A2) were recorded extracellularly. The impulse activity of both receptor units rises beyond resting activity when stimulated by airborne sound. |
2. | The time course of the excitation of both receptor units appears to be phasic-tonic (Fig. 4). |
3. | The influence of stimulus intensity and its time course on the excitation of both receptor units was studied (Figs. 5–8). |
4. | The threshold curves of the receptor units Al and A2 for airborne sound were determined in the frequency range between 0.3 to 20 kHz. The two receptor units differ. Receptor unit Al shows a distinct threshold minimum, whereas the threshold curve of the less sensitive receptor units A2 appears more flat (Fig. 9). |
5. | The threshold curves of the receptor units on the left body side differ from those on the right. The threshold minimum of unit Al left is absolutely lower than that of Al right and lies at higher frequencies (Fig. 10). |
6. | As observed under the light microscope, vibrations of the organ's base and bulb differ from one side of the body to the other (Fig. 11). |
7. | Removing the bulb influences the mode of oscillation of the base as well as the threshold curves of the receptor units. |
8. | A hypothesis is proposed regarding the function of integumentary structures on the membrane in stimulus transformation. |
5.
Hans Machemer Sigrun Machemer-Röhnisch Richard Bräucker Keiichi Takahashi 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1991,168(1):1-12
1. | We have investigated a physiological component of the gravitaxis of Paramecium using established mechanisms of ciliate mechanosensitivity. The horizontal, up and down swimming rates of cells, and the sedimentation of immobilized specimens were determined. Weak DC voltage gradients were applied to predetermine the Paramecium swimming direction. |
2. | An observed steady swimming rate is the vector sum of active propulsion (P), a possible gravity-dependent change in swimming rate (), and rate of sedimentation (S). We approximated P from horizontal swimming. S was measured after cell immobilization. |
3. | Theory predicts that the difference between the down and up swimming rates, divided by two, equals the sum of S and . is supposed to be the arithmetic mean of two subcomponents, a and p, from gravistimulation of the anterior and posterior cell ends, respectively. |
4. | A negative value of (0.038 mm/s) was isolated with a(0.070 mm/s) subtracting from downward swimming, and p(0.005 mm/s) adding to upward propulsion. The data agree with one out of three possible ways of gravisensory transduction: outward deformation of the mechanically sensitive lower soma membrane. We call the response a negative gravikinesis because both a and p antagonize sedimentation. |
6.
R. Sidikou-Seyni C. Rambaud J. Dubois J. Vasseur 《Plant Cell, Tissue and Organ Culture》1992,29(2):83-91
Somatic embryos and adult plants were regenerated from mesophyll protoplasts of a clone of chicory 474 (Cichorium intybus L. x Cichorium endivia L.). Embryos were obtained in three different ways:
Development of embryos was accomplished in agitated liquid Heller medium with 0.15 M gibberellic acid and germination on solid Heller medium without growth regulators. The total time for plantlet (4-leaves stage) recovery, following protoplast isolation, was 13 to 15 weeks. After acclimatization all protoplast-derived plants of Cichorium 474 were phenotypically normal and fertile. 相似文献
| - plating of 7-day-old protoplast cultures on PM-3 solid induction medium with 2.5 M 2-isopentenyladenine (2-iP) and 0.5 M naphthaleneacetic acid (NAA); |
| - transfer of 1–2 mm microcolonies into liquid M-17 induction medium with 2.5 M (2-iP) and 0.1 M (NAA); |
| - transfer of well-established protoplast-derived calluses onto M-17. |
7.
Peter W. Sorensen Toshiaki J. Hara Norman E. Stacey Joseph G. Dulka 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1990,166(3):373-383
1. | To determine the specificity of the goldfish (Carassius auratus) olfactory system to the reproductive pheromone 17,20-dihydroxy-4-pregnen-3-one (17,20P), and to determine if related sex steroids might also function as pheromones, electro-olfactogram (EOG) responses were recorded from mature male goldfish. |
2. | Of the 24 steroids tested, 17,20P was the most stimulatory. It had a detection threshold of 10–12 M and at a concentration of 10–8 M elicited an EOG response 3 times that elicited by 10–5 M L-serine |
3. | 17,20,21-triol-4-pregnen-3-one, a metabolite of 17,20P, was the only other highly stimulatory steroid. Its threshold was 10–11 M. |
4. | In cross-adaptation experiments EOG responses to all 21-carbon steroids were inhibited during adaptation to 17,20P: responses to this pheromone are transduced by a single receptor/transduction mechanism. |
5. | To verify the biological relevance of EOG recording whole animal responsiveness was determined by measuring blood gonadotropin. When goldfish were placed into homogeneous steroid solutions endocrine responsiveness strongly correlated with EOG recording. However, when steroids were added to aquaria containing fish, responses were less specific indicating that transient wisps of steroids trigger endocrine responses. |
6. | Although the extreme sensitivity and specificity of the goldfish olfactory system to 17,20P gives it the potential to serve as a highly specific cue, realization of this potential is probably determined by the dynamics of pheromone exposure. |
8.
W. A. Berzonsky R. L. Clements H. N. Lafever 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1991,81(5):629-634
One cultivar (GR876) and two advanced Ohio soft red winter wheat lines (OH413 and OH414), with Kavkaz in their pedigrees, were examined for the presence of the Kavkaz, 1RS/1BL rye/wheat chromosome translocation. Another advanced line (OH416), with Amigo in its pedigree, was examined for the presence of the Amigo, 1RS/1AL translocation. Only two satellited chromosomes were observed in most mitotic root-tip cells from GR876, OH413, and OH414, compared to four in most cells from OH416. Heteromorphic bivalents were observed in most PMCs from hybrids produced by crossing GR876, OH413, and OH414 as females to Chinese Spring. No heteromorphic bivalents were observed in PMCs from OH416 x Chinese Spring hybrids. When GR876 and the Ohio lines were hybridized with Chinese Spring dimonotelosomic-1B, telosomic trivalents, consisting of the short- and longarm telosomes paired with chromosome 1B, were only observed in PMCs from 43-chromosome hybrids involving OH416. The long-arm telosome paired with the translocation chromosome, while the short-arm telosome remained unpaired in all other 43-chromosome hybrids. Separation of gliadin proteins from GR876 and the Ohio lines by PAGE revealed that secalin bands for GR876, OH413, and OH414, migrated similarly to the secalins for Kavkaz. Bands for OH416, identified as possible secalins, migrated similarly to those for Amigo. Cultivar GR876 and advanced Ohio soft red winter wheat lines OH413 and OH414 carry the Kavkaz translocation, while OH416 carries the Amigo translocation.Communicated by K. Tsunewaki 相似文献
9.
Eliezer E. Goldschmidt 《Plant Growth Regulation》1984,2(1):9-13
The relationship of abscisic acid (ABA) and 2-trans-abscisic acid (t-ABA) to alternate bearing has been examined in Wilking mandarin (Citrus reticulata Blanco) trees. Leaves, stems and buds of trees loaded with fruit (on trees) had 4.3, 6.0 and 2.2 fold higher ABA levels than the corresponding organs from off trees. Leaves had higher ABA levels than stems and buds in both on and off trees. t-ABA was non-detectable in Wilking leaf, stem and bud tissue. Amounts of t-ABA not exceeding 40% of the ABA content, were found in Shamouti and Valencia orange buds and in Wilking fruit peel.The elevated levels of ABA in on tree organs may reflect a stress imposed by the fruit overload. 相似文献
10.
Daniela Bratosin Joel Mazurier Henri Debray Myriam Lecocq Benoni Boilly Catherine Alonso Magdalena Moisei Cecilia Motas Jean Montreuil 《Glycoconjugate journal》1995,12(3):258-267
Comparing the properties of young and senescent (aged) O+ erythrocytes isolated by applying ultracentrifugation in a self-forming Percoll gradient, we demonstrate that the sialic acids of membrane glycoconjugates control the life span of erythrocytes and that the desialylation of glycans is responsible for the clearance of the aged erythrocytes. This capture is mediated by a -galactolectin present in the membrane of macrophages. The evidence supporting these conclusions is as follows:
These results were presented at the Jacques Monod Conference on Glycoconjugates (La Londe-les-Maures, 25–29 April 1994) and at the International Conference Romania and Romanians in Contemporary Science (Sinaia, 24–27 May 1994). 相似文献
(1) | Analysis by flow cytofluorimetry of the binding of fluorescein isothiocyanate labelled lectins specific for sialic acids shows that the aged erythrocytes bind less WGA, LPA, SNA and MAA than young erythrocytes. The binding of DSA and LCA is not modified. On the contrary, the number of binding sites of UEA-I specific for O antigen and of AAA decreases significantly. PNA and GNA do not bind to erythrocytes. |
(2) | RCA120 as well asErythrina cristagalli andErythrina corallodendron lectins specific for terminal -galactose residues lead to unexpected and unexplained results with a decrease in the number of lectin binding sites associated with increasing desialylation. |
(3) | The glycoconjugates from the old erythrocytes incorporate more sialic acid than the young cells. This observation results from the determination of the rate of transfer by -2,6-sialyltransferase of fluorescent or radioactiveN-acetylneuraminic acid, using as donors CMP-9-fluoresceinyl-NeuAc and CMP-[14C]-NeuAc, respectively. |
(4) | Microscopy shows that the old erythrocytes are captured preferentially by the macrophages relative to the young ones. Fixation of erythrocytes by the macrophage membrane is inhibited by lactose, thus demonstrating the involvement of a terminal -galactose specific macrophage lectin. |
(5) | Comparative study of the binding of WGA, LPA, SNA and MAA to the aged erythrocytes and to thein vitro enzymatically desialylated erythrocytes shows that the desialylation rate of aged cells is low but sufficient to lead to their capture by the macrophages |
11.
K. S. Olson C. D. Derby 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1995,176(4):527-540
1. | The effects of the odorant compounds adenosine-5-monophosphate (5AMP), ammonium, betaine, L-cysteine, L-glutamate, DL-succinate, and taurine and of mixtures of these comounds on binding of taurine and 5AMP to dendritic membrane from the olfactory organ of spiny lobsters (Panulirus argus) were quantified to evaluate the contribution of inhibition of odorant-receptor binding to the generation of physiological responses to mixtures. |
2. | Taurine binding sites belong to two affinity classes, while 5AMP binding sites belong to a single affinity class. Binding of either taurine or 5AMP was partially inhibited in an apparently noncompetitive, concentration dependent fashion by most odorant compounds, with 25–40 % inhibition by 1 mM of odorant. Mixtures of two or more odorant compounds also inhibited binding of taurine or 5AMP to its sites. However, the inhibition by mixtures was often significantly less than expected from the inhibition produced by a mixture's components assuming either a noncompetitive or competitive mechanism. |
3. | By including this binding inhibition between compounds into models for predicting physiological responses to mixtures from the responses to the components, the predictive power of the models is significantly improved. This result strongly suggests that binding inhibition can influence the physiological responsiveness of chemoreceptor cells to mixtures. |
12.
Ellen Thaler 《Journal of Ornithology》1976,117(2):121-144
Beobachtungen über Nest und Nestbautechnik von Winter- und Sommergoldhähnchen(Regulus regulus, R. ignicapillus) im Freiland und in Volieren zeigen:
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1. | Die Neststandorte von WG und SG gleichen einander, ihre Brutreviere können sich überlappen. |
2. | Das Nest zeigt 3 deutlich getrennte Schichten. Die Außenschicht besteht aus Spinnstoff, Moos, Flechten — Moose (bei WG auch Flechten) bilden die Mittelschicht, Federn und Haare die Polsterung. Hochgebirgsnester weisen gegenüber Mittelgebirgsnestern einen Materialzuwachs besonders in der Mittel- und Polsterschicht auf. |
3. | Der Nestbau dauert ca. 20 Tage, Zweitnester können rascher entstehen. |
4. | Die Bautechnik wechselte mit fortschreitendem Bau. Baubewegungen für Grundgerüst, Rohbau und Polsterung waren verschieden. 14 (WG) bis 15 (SG) Baubewegungen konnten unterschieden und den 3 Bauphasen zugeordnet werden: a) Bei der Anlage des Grundgerüsts wurden die Tragästchen mit Spinnstoff bedeckt/umwickelt. Die Gespinste wurden dabei abgerieben, verspannt, und beim Außen säubern mit dem Ast fest verbunden. b) Der Rohbau entstand durch weiteres Einbringen von Spinnstoff und zunehmend häufiger Moosen/Flechten. Die Wände wurden durch Wegschieben (bzw. Einvibrieren) der Baustoffe geformt und gefestigt, beim WG auch maskiert, der Boden durch Unten säubern geschlossen. Zuletzt eingestopfte Moose der Mittelschicht wurden verstrampelt, der Rand durch Verstreichen verstärkt und geglättet. c) Die Mulde wurde mit Federn/Haaren ausgekleidet, das Polstermaterial durch Strampeln geordnet, sperrige oder auffallende Polsterstoffe wieder entfernt. Gleichzeitig wurde der Nestrand eng zusammengezogen, die Tragästchen von Spinnstoffresten gesäubert; SG verdeckten durch aufgesteckte Federn die Nestmulde. |
5. | Die beiden Arten stimmten auch in ihrer Nestbautechnik weitgehend überein. Auffälligster Unterschied war, daß sich SG am Nestbau nicht beteiligen und nur begleiten. Doch führten juvenile beider Arten fast alle Baubewegungen spielerisch aus. Unterschiede gab es auch in den Baubewegungen der : SG vibrierten beim Wegschieben (2 e) und Randverstreichen (2 g) und verdeckten die Mulde durch aufgesteckte Federn. |
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Kate M. Boothby Alan Roberts 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1992,170(2):171-180
1. | When Xenopus laevis embryos swim into an obstruction they usually stop. This stopping response to stimulation on the head is present from stage 28 to 45. At stage 37/38 it is more reliable in restrained than in free-swimming animals, and to stimuli to the cement gland than to the head skin. Fictive swimming also stops reliably after the same stimuli but struggling and fictive struggling do not. |
2. | Discharge of deformation-sensitive trigeminal sensory neurons in response to pressure on the cement gland or head skin precedes the fictive stopping response. When the embryo hangs from cement gland mucus, trigeminal neurons are active and the embryo is less responsive to stimulation. |
3. | Lesions of the central nervous system have allowed us to draw the following conclusions about this inhibitory pathway: (a) either the cement gland or the head skin must be intact; (b) one trigeminal ganglion is both sufficient and necessary; (c) the pathway is independent of the forebrain and midbrain; (d) it can take an ipsilateral or contralateral route through the hindbrain; (e) at least two hindbrain interneuron components are involved. |
4. | A similar stopping response is present in embryos and larvae of the urodele Ambystoma mexicanum. |
15.
J. A. Thompson Ampan Bhromsiri Arawan Shutsrirung Srisook Lillakan 《Plant and Soil》1991,135(1):53-65
Over 1500 root-nodule bacteria were isolated from a range of uninoculated soybeans, and one cowpea, trap-hosts, sown in 1985 into traditional soybean-growing areas of soybean-growing areas of northern Thailand. Most isolates were slow-growing Bradyrhizobium japonicum. Using a modified bottle-jar technique, 586 of the isolates were tested with a range of soybean hosts and one cowpea host. The results indicated:
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(a) | a very high level of infectiveness, with only one isolate failing to nodulate one host, and 95% forming \s>20 nodules per plant; |
(b) | a high level of effectiveness of fixation of nitrogen by the local rhizobium populations with soybeans; |
(c) | evidence of selection of effective strains by both soybean and cowpea hosts in the field; |
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Krzysztof Wypijewski Teresa Duda Rameshwar K. Sharma 《Molecular and cellular biochemistry》1995,144(2):181-190
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Source water used by plants of several species in a semi-evergreen lowland tropical forest on Barro Colorado Island, Panama, was assessed by comparing the relative abundance of deuterium, D, versus hydrogen, H (stable hydrogen isotope composition, D) in xylem sap and in soil water at different depths, during the dry season of 1992. Ecological correlates of source water were examined by comparing xylem water D values with leaf phenology, leaf water status determined with a pressure chamber, and rates of water use determined as mass flow of sap using the stem heat balance method. Soil water D values decreased sharply to 30 cm, then remained relatively constant with increasing depth. Average D values were-13, for 0–30 cm depth and-36.7 for 30–100 cm depth. Soil water D values were negatively associated with soil water content and soil water potential. Concurrent analyses of xylem water revealed a high degree of partitioning of water resources among species of this tropical forest. Xylem water D of deciduous trees (average=-25.3±1.4) was higher than that of evergreen trees (average=-36.3±3.5), indicating that evergreen species had access to the more abundant soil water at greater depth than deciduous species. In evergreen shade-tolerant and high-light requiring shrubs and small trees, D of xylem water was negatively correlated with transpiration rate and leaf water potential indicating that species using deeper, more abundant water resources had both higher rates of water use and more favorable leaf water status. 相似文献