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81.
82.
W. W. Schwippert T. W. Beneke J. P. Ewert 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1990,167(4):509-520
Summary Intracellular recording and labeling of cells from the toad's (Bufo bufo spinosus) medulla oblongata in response to moving visual (and tactual) stimuli yield the following results. (i) Various response types characterized by extracellular recording in medullary neurons were also identified intracellularly and thus assigned to properties of medullary cell somata. (ii) Focussing on monocular small-field and cyclic bursting properties, somata of such neurons were recorded most frequently in the medial reticular formation and in the branchiomotor column but less often in the lateral reticular formation. (iii) Visual object disrimination established in pretectal/tectal networks is increased in its acuity in 4 types of medullary small-field neurons. The excitatory and inhibitory inputs to these neurons evoked by moving visual objects suggest special convergence likely to increase the filter properties. (iv) Releasing conditions, temporal pattern, and refractoriness of cyclic bursting neurons resemble membrane characteristics of vertebrate and invertebrate neurons known to play a role in premotor/motor activity. (v) Integrating functions of medullary cells have an anatomical correlate in the extensive arborizations of their dendritic trees; 5 morphological types of medullary neurons have been distinguished.Abbreviations
A
stripe moving in antiworm configuration
- (W)
moving in worm configuration
-
S
square
-
BMC
branchiomotor column
-
EPSP
excitatory postsynaptic potential
-
IPSP
inhibitory postsynaptic potential
-
RetF
medullary reticular formation
-
RF
receptive field
-
M neurons
response properties of medullary neurons
-
T neurons
classes of tectal neurons
-
TH neurons
classes of thalamic/pretectal neurons
-
tr.tb.d.
tractus tecto-bulbaris directus
-
tr.tbs.c.
tractus tecto-bulbaris et spinalis cruciatus 相似文献
83.
A sensitive and specific radioimmunoassay (RIA) for the oxidised form of methionine5-enkephalin (Met5-Enk), Met5-Enk sulphoxide (Met5-Enk-S), has been developed. Antisera were raised in rabbits against Met5-Enk coupled to carrier proteins with glutaraldehyde or carbodiimide. Displacement of (125I) Met5-Enk bound to antiserum by Met5-Enk was poor, but Met5-Enk-S displayed good displacement suggesting that the Met5-Enk immunogen was oxidised to Met5-Enk-S and that the antisera were formed against this compound. The sensitivity of the RIA for Met5-Enk-S was 0.02 pmole/tube using the most sensitive antiserum. The antisera showed negligible cross-reactivity with leucine5-enkephalin and with both native and oxidised endorphins. Cross-reactivity was between 15% and 28% with the fragment Met5-Enk (2–5) sulphoxide and between 9% and 25% with D-Ala2-Met5-Enk sulphoxide. The antisera showed<0.01% cross-reactivity with other Met5-Enk fragments and naturally occurring neuropeptides. Tissue extracts were oxidised with hydrogen peroxide prior to assay. Met5-Enk-S immunoreactivity (IMR) was detected in brain, pituitary gland, pancreas, and intestine extracts of the rat, chicken, toad and teleost, and in cerebral-suboesophageal ganglion extracts of the snail. All tissue extracts showed parallelism in serial dilution to synthetic mammalian Met5-Enk-S, suggesting possible immunological identity. The results indicate that spontaneous oxidation of Met5-Enk immunogen occurs such that antisera are produced against the sulphoxide analogue of Met5-Enk, and may account for the relative insensitivity of some published RIAs using Met5-Enk standard. Our findings demonstrate a wide phylogenetic and anatomical distribution of Met5-Enk IMR. 相似文献
84.
85.
M. Glagow J.-P. Ewert 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1996,180(1):1-9
This study confirms for a phylogenetically basal terrestrial vertebrate that dopaminergic modulations interfere with the
visually directed appetitive and consummatory feeding behaviors orienting and snapping, respectively. (1) In common toads
Bufo bufo, intralymphatic administration of the dopamine D2/D1-receptor agonist apomorphine led to a dose-dependent facilitation of prey-snapping in response to moving objects. The snapping
activity reached a maximum 15–35 min after apomorphine injection. (2) To changes in configurational stimulus features, the
basic pattern of discrimination was maintained; however, the acuity of discrimination was reduced due to the high snapping
response level. (3) The apomorphine-induced facilitation of snapping was accompanied by a suppression of prey-oriented lunging
and turning. Toads snapped only if prey occurred frontally in the visual field at a relatively short distance. The snapping
behavior was fixed in its form and stereotyped regarding its immediate release. (4) About 90 min after apomorphine administration,
prey-oriented turning behavior was restored and displayed a facilitatory rebound. (5) In comparative experiments with the
species B. marinus, both prey-oriented turning and snapping responses were suppressed by apomorphine in a dose-dependent manner. (6) After pre-treatment
with the dopamine antagonist haloperidol, apomorphine showed no measurable effect on the visual release of prey orienting
or snapping. (7) The results contribute to the sensorimotor and the motivation hypothesis of dopamine function proposed for
higher vertebrates and stimulate a comparative discussion of anatomic homologies and functional analogies.
Accepted: 10 July 1996 相似文献
86.
Osmotic permeabilities of several epithelial structures have been determined with novel optical procedures based on specular microscopy. The osmotic permeabilities of several tissue layers were determined by continuously monitoring the position of the apical tissue borders while an osmotic flow was imposed across those layers. The values found were (in μm/s; mean ± SE): corneal epithelium, 137 ± 30 (n = 5); antidiuretic hormone stimulated toad bladder, 429 ± 64 (n = 6); and corneal endothelium, 711 ± 34 (n = 7). In addition, the osmotically-induced transient change in thickness of the corneal endothelial cells was determined with the help of a computer, and the apparent osmotic permeability measured for the apical membrane was 1420 ± 160 μm/s (n = 5). It is concluded that the osmotic permeability across the endothelial layer is sizably larger than had been previously detected and that osmotic flows across such layer largely traverse the cellular membranes. With osmotic permeability values (per unit of cell membrane area) as large as presently reported, isotonic fluid transport by epithelia can be explained simply on the basis of local osmotic gradients. 相似文献
87.
R. Toriano P. Ford V. Rivarola B.K. Tamarappoo A.S. Verkman M. Parisi 《The Journal of membrane biology》1998,161(2):141-149
Transepithelial water permeability was measured in LLC-PK1 cells stably transfected with aquaporins (AQPs): AQP1, AQP2, and
a chimera of AQP1 and AQP2 containing 41 amino acids of the C-terminus of AQP2. Transepithelial water fluxes (Jw) were not
previously reported in cells transfected with aquaporins. Jw were now recorded each minute using a specially developed experimental
device. A significant increase in Posm after forskolin (FK) plus vasopressin (VP) was found in AQP2 transfected cells (39.9
± 8.2 vs. 12.5 ± 3.3 cm · sec−1· 10−3), but not in cells transfected with AQP1 (15.3 ± 3.6 vs. 13.4 ± 3.6 cm · sec−1· 10−3). In the case of the AQP1/2 cells (chimera) the FK plus VP induced Posm was smaller than in AQP2 cells but significantly
higher than in mock cells at rest (18.1 ± 4.8 vs. 6.7 ± 1.0 cm · sec−1· 10−3). The increases in Posm values were not paralleled by increases in 14C-Mannitol permeability. HgCl2 inhibited the hydrosmotic response to FK plus VP in AQP2 transfected epithelia. Results were comparable to those observed,
in parallel experiments, in a native ADH-sensitive water channel containing epithelial barrier (the toad urinary bladder).
Electron microscopy showed confluent LLC-PK1 cells with microvilli at the mucosal border. The presence of spherical or elongated
intracellular vacuoles was observed in AQP2 transfected cells, specially after FK plus VP stimulus and under an osmotic gradient.
These results demonstrate regulated transepithelial water permeability in epithelial cells transfected with AQP2.
Received: 24 June 1997/Revised: 16 September 1997 相似文献
88.
Cane Toads (Rhinella marina, formerly Bufo marinus) in restoration sites on the Atherton Tableland in NE Australia consumed invertebrates belonging to 11 different taxa with ants being the most abundant prey item. Principal component analyses showed that the composition of invertebrates in Cane Toad diet is largely a reflection of invertebrates found in pitfall and leaf litter samples suggesting that the species is an indiscriminant feeder. However, pitfall samples contained more Collembola and Isopoda than were found in Cane Toad stomachs. The Cane Toad may benefit from restoration management practices by utilizing food resources enhanced by mulching and providing microhabitats (e.g. rock piles, logs) as shelter. While further studies would be needed to test this practitioners working in areas where the Cane Toad is problematic may consider trade‐offs between attracting invertebrates and Cane Toads by monitoring provided microhabitat features. 相似文献
89.
In the study of active transport it is important to distinguish between oxygen consumption sustaining transepithelial transport and that responsible for other tissue functions (basal metabolism). Since amiloride blocks transepithelial active sodium transport and the associated oxygen consumption in the frog skin and toad bladder, we and others have employed this agent to evaluate the rate of basal metabolism. This technique has recently been criticized in a report that amiloride (and ouabain) increased oxygen consumption when no sodium was available for transport. We have been unable to corroborate these observations.With magnesium-Ringer as external bathing solutions, amiloride and ouabain failed to stimulate oxygen consumption. With sodium-Ringer as external bathing solution amiloride reduced oxygen consumption about 30%, to a level indistinguishable from that found on external substitution of magnesium-Ringer for sodium-Ringer. We conclude that the use of amiloride permits evaluation of the rate of basal metabolism with acceptable accuracy; a possible slight depressant effect of ouabain on basal metabolism remains to be investigated. 相似文献