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  • 1
    Electronic Resource
    Electronic Resource
    Outwardly rectifying chloride channels in lymphocytes (1992)
    Springer
    The journal of membrane biology 127 (1992), S. 49-56 
    Details
    ISSN: 1432-1424
    Keywords: chloride channel ; lymphocyte ; outward rectification ; temperature ; regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Outwardly rectifying Cl− channels in cultured human Jurkat T-lymphocytes were activated by excising a patch of membrane using the inside-out (i/o) patch-clamp configuration and holding at depolarized voltages for prolonged periods of time (1–6 min at +80 mV, 20°C). The single-channel current at +80 mV was 4.5 ± 0.3 pA and at −80 mV, it was 1.0 ± 0.4 pA. After activation, the probability of being open (P 0)for the lymphocyte channel was voltage independent. Activation of the Cl− channel in lymphocytes was temperature dependent. Nineteen percent of i/o recordings from lymphocytes made at 20°C exhibited Cl− channel activity. In contrast, 49% of recordings made at 30°C showed channel activity. The number of channels in an active patch was not significantly different at the two temperatures. Channel activation in excised, depolarized patches also occurred 20-fold faster at 30°C than at 20°C. There was no marked change in the single-channel conductance at 30°C. Open-channel conductance was blocked by 200 μm indanyloxyacetic acid (IAA) or 1 mm SITS when applied to the intracellular side of the patch. The characteristics of this channel are similar to epithelial outwardly rectifying Cl− channels thought to be involved in fluid secretion
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00232757
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  • 2
    Electronic Resource
    Electronic Resource
    Cl− channels in intact human T lymphocytes (1992)
    Springer
    The journal of membrane biology 125 (1992), S. 171 
    Details
    ISSN: 1432-1424
    Keywords: chloride channel ; cell-attached patches ; lymphocyte ; T cell ; temperature ; voltage dependence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary We recently described a large, multiple-conductance Cl− channel in excised patches from normal T lymphocytes. The properties of this channel in excised patches are similar to maxiCl− channels found in a number of cell types. The voltage dependence in excised patches permitted opening only at nonphysiological voltages, and channel activity was rarely seen in cell-attached patches. In the present study, we show that Cl− channels can be activated in intact cells at physiological temperatures and voltages and that channel properties change after patch excision. Maxi-Cl− channels were reversibly activated in 69% of cellattached patches when the temperature was above 32°C, whereas fewer than 2% of patches showed activity at room temperature. Upon excision, the same patches displayed large, multiple-conductance Cl− channels with characteristics like those we previously reported for excised patches. After patch excision, warm temperatures were not essential to allow channel activity; 37% (114/308) of inside-out patches had active channels at room temperature. The voltage dependence of the channels was markedly different in cell-attached recordings compared with excised patches. In cell-attached patches, Cl− channels could be open at cell resting potentials in the normal range. Channel activation was not related to changes in intracellular Ca2+ since neither ionomycin nor mitogens activated the channels in cell-attached patches, Ca2+ did not rise in response to warming and the Cl− channel was independent of Ca2+ in inside-out patches. Singlechannel currents were blocked by internal or external Zn2+ (100–200 μm), 4-acetamido-4′ isothiocyanostilbene-2,2′-disulfonate (SITS, 100–500 μm) and 4,4′-diisothiocyanostilbene 2,2′disulfonate (DIDS, 100 μm). NPPB (5-nitro-2-(3-phenylpropylamino)-benzoate) reversibly blocked the channels in inside-out patches.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233356
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  • 3
    Electronic Resource
    Electronic Resource
    Response of chloride efflux from skeletal muscle ofRana pipiens to changes of temperature and membrane potential and diethylpyrocarbonate treatment (1991)
    Springer
    The journal of membrane biology 123 (1991), S. 223-233 
    Details
    ISSN: 1432-1424
    Keywords: skeletal muscle ; Cl− efflux ; Cl− channel ; pH ; muscle membrane ; temperature ; diethylpyrocarbonate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Efflux of36Cl− from frog sartorius muscles equilibrated in two depolarizing solutions was measured. Cl− efflux consists of a component present at low pH and a pH-dependent component which increases as external pH increases. For temperatures between 0 and 20°C, the measured activation energy is 7.5 kcal/mol for Cl− efflux at pH 5 and 12.6 kcal/mol for the pH-dependent Cl− efflux. The pH-dependent Cl− efflux can be described by the relationu=1/(1+10n(pK a -pH)), whereu is the Cl− efflux increment obtained on stepping from pH 5 to the test pH, normalized with respect to the increment obtained on stepping from pH 5 to 8.5 or 9.0. For muscles equilibrated in solutions containing 150mm KCl plus 120mm NaCl (internal potential about −15 mV), the apparent pK a is 6.5 at both 0 and 20°C, andn=2.5 for 0°C and 1.5 for 20°C. For muscles equilibrated in solutions containing 7.5mm KCl plus 120mm NaCl (internal potential about −65 mV), the apparent pK a at 0°C is 6.9 andn is 1.5. The voltage dependence of the apparent pK a suggests that the critical pH-sensitive moiety producing the pH-dependent Cl− efflux is sensitive to the membrane electric field, while the insensitivity to temperature suggests that the apparent heat of ionization of this moiety is zero. The fact thatn is greater than 1 suggests that cooperativity between pH-sensitive moieties is involved in determining the Cl− efflux increment on raising external pH. The histidine-modifying reagent diethylpyrocarbonate (DEPC) applied at pH 6 reduces the pH-dependent Cl− efflux according to the relation, efflux=exp(−k·[DEPC]·t), wheret is the exposure time (min) to DEPC at a prepared initial concentration of [DEPC] (mm). At 17°C,k −1=188mm·min. For temperatures between 10 and 23°C,k has an apparent Q10 of 2.5. The Cl− efflux inhibitor SCN− at a concentration of 20mm substantially retards the reduction of the pH-dependent Cl− efflux by DEPC. The findings that the apparent pK a is 6.5 in depolarized muscles, that DEPC eliminates the pH-dependent Cl− efflux, and that this action is retarded by SCN− supports the notion that protonation of histidine groups associated with Cl− channels is the controlling reaction for the pH-dependent Cl− efflux.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01870405
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  • 4
    Electronic Resource
    Electronic Resource
    Sensitivity of Trichoplusia ni (Hübner) pheromone receptor neurons: Relationships between neural thresholds and behavioral responses (1991)
    Springer
    Journal of comparative physiology 168 (1991), S. 739-747 
    Details
    ISSN: 1432-1351
    Keywords: Threshold ; Olfaction ; Insect ; Lepidoptera ; Noctuid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Responses of Trichoplusia ni HS(A) receptor neurons were measured to determine the minimum detectable concentration (absolute threshold) and the minimum detectable increment (difference threshold) for the major sex pheromone component (Z)-7-dodecen-1-ol acetate (Z7-12∶Ac). The absolute threshold was 1000-fold below the ∼10-11 M level of Z7-12∶Ac at a calling female. The Weber fraction, i.e., the ratio of the difference threshold to the stimulus concentration, declined from ∼0.8 to ∼0.06 as the concentration rose from threshold to high intensities. Relatively smaller fluctuations were detected as the stimulus increased. 2. The HS(A) responses were interpreted in relation to behavior by considering an ideal observer as approximating the central nervous system (CNS). The ideal thresholds were 3–9-fold lower than the HS(A) thresholds. 3. The ideal absolute threshold of the T. ni CNS is comparable to observed behavioral thresholds for wingflutter and taking flight. However, only a low percentage response occurs at threshold. Most males take flight at higher concentrations. Also, the ideal Weber fraction is lower than in most flight-tunnel bioassays. Yet, males respond to small fluctuations in orienting to pheromone plumes. These differences between moths and ideal observers may reflect inhibition at points in the CNS that control the flow of olfactory input.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00224362
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  • 5
    Electronic Resource
    Electronic Resource
    Digestion of uncrushed leaf tissues by leaf-snipping larval Lepidoptera (1992)
    Springer
    Oecologia 89 (1992), S. 229-235 
    Details
    ISSN: 1432-1939
    Keywords: Lepidoptera ; Digestion ; Larvae ; Mandible ; C4 grasses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Cynodon dactylon (Poaceae) leaf pieces recovered from the frass of final-instar Paratrytone melane larvae (Lepidoptera: Hesperiidae) were composed of 14–22 percent crushed cells and 78–86 percent uncrushed cells, yet approximate digestibilities of soluble carbohydrates and protein averaged 78 and 88 percent, respectively. Therefore, nutrients from uncrushed cells were extracted by P. melane. The ability of P. melane and another leaf-snipping lepidopteran, Pseudaletia unipuncta (Noctuidae), to digest the contents of uncrushed bundle sheath and mesophyll cells in C. dactylon was examined with transmission electron microscopy. Organelles and plasma membranes were digested in the foreguts and midguts of both species. These findings suggest that nutrients in uncrushed leaf cells may be extracted through plasmodesmata and cell wall pores after membranes are digested. The generality of leaf-snipping, vis-a-vis leaf crushing, among larval Lepidoptera was assessed by surveying the mandible morphologies of 202 species. In 82 percent of the species surveyed only incisor regions were present. I conclude that leaf-snipping is a common mode of feeding among phytophagous Lepidoptera and that the digestion of cell contents is efficient despite the fact that few of the cells of ingested plant tissues are crushed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317222
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  • 6
    Electronic Resource
    Electronic Resource
    Determinants of predation on phytophagous insects: the importance of diet breadth (1993)
    Springer
    Oecologia 96 (1993), S. 575-582 
    Details
    ISSN: 1432-1939
    Keywords: Diet specialization ; Host plant chemistry ; Lepidoptera ; Paraponera clavata ; Predation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To evaluate the role of predation in the evolution of diet specialization and to determine the effectiveness of various larval defenses, we offered lepidopteran larvae to colonies of the tropical ant Paraponera clavata. We recorded behavioral and physical characteristics of prey items and used log-linear models to analyze their importance as deterrents to predation by P. clavata. The most important determinant of probability of prey rejection by P. clavata was a prey's diet breadth; specialists were rejected by the ants significantly more than generalists. Other less important, but significant, predictors of prey rejection included ontogeny, morphology and chemistry. Late instar caterpillars were rejected more frequently than early instars, hairy caterpillars were rejected more frequently than caterpillars with other morphologies, and one caterpillar species with an unpalatable extract was rejected more frequently than two species with palatable extracts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00320516
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  • 7
    Electronic Resource
    Electronic Resource
    Relative nutritional quality of C3 and C4 grasses for a graminivorous lepidopteran, Paratrytone melane (Hesperiidae) (1992)
    Springer
    Oecologia 92 (1992), S. 97-103 
    Details
    ISSN: 1432-1939
    Keywords: C3 and C4 grasses ; Lepidoptera ; Hesperiidae ; Paratrytone melane ; Nutrients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We tested the hypothesis that C4 grasses are inferior to C3 grasses as host plants for herbivorous insects by measuring the relative performance of larvae of a graminivorous lepidopteran, Paratrytone melane (Hesperiidae), fed C3 and C4 grasses. Relative growth rates and final weights were higher in larvae fed a C3 grass in Experiment I. However, in two additional experiments, relative growth rates and final weights were not significantly different in larvae fed C3 and C4 grasses. We examined two factors which are believed to cause C4 grasses to be of lower nutritional value than C3 grasses: foliar nutrient levels and nutrient digestibility. In general, foliar nutrient levels were higher in C3 grasses. In Experiment I, protein and soluble carbohydrates were digested from a C3 and a C4 grass with equivalent efficiencies. Therefore, differences in larval performance are best explained by higher nutrient levels in the C3 grass in this experiment. In Experiment II, soluble carbohydrates were digested with similar efficiencies from C3 and C4 grasses but protein was digested with greater efficiency from the C3 grasses. We conclude (1) that the bundle sheath anatomy of C4 grasses is not a barrier to soluble carbohydrate digestion and does not have a nutritionally significant effect on protein digestion and (2) that P. melane may consume C4 grasses at compensatory rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317268
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  • 8
    Electronic Resource
    Electronic Resource
    Localization of spectral receptors in the ommatidium of butterfly compound eye determined by polarization sensitivity (1992)
    Springer
    Journal of comparative physiology 171 (1992), S. 289-297 
    Details
    ISSN: 1432-1351
    Keywords: Electrophysiology ; Lepidoptera ; Photoreceptor ; Spectral sensitivity ; Vision
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. A butterfly Papilio has 5 types of spectral receptors in the compound eye. The spectral sensitivity of each type peaks in the UV, violet, blue, green, and red wavelengths, respectively. The green type contains two subtypes with and without a UV secondary peak. Here we studied the localization of these spectral receptors within the ommatidium. 2. An ommatidium contains 9 photoreceptors (R1–9), each of which is one of the 5 spectral receptor types. The photoreceptors bear parallel microvilli to form a nontwisted rhabdom, and thereby the photoreceptors are polarization sensitive. 3. We first examined the microvillar orientation by electron microscopy. The microvilli of R1, 2, and 9 are oriented dorso-ventrally (0°), whereas those of R3 and 4 are parallel to the antero-posterior axis (90°). The R5–8 bear microvilli diagonally: 45° for R6 and R8, 135° for R5 and R7. 4. We then recorded spectral and polarization sensitivities from single photoreceptors. The peak angle of the polarization sensitivity (θmax) of the UV, violet, and blue receptors were around 0°, whereas that of the green receptors was around 90°. In the double-peaked green receptors, the θmax at UV was also around 90°. The red receptors showed a θmax at around 35°. The polarization sensitivity ratio (PSmax/PSmin) of the double-peaked green receptors measured at UV was around 4, whereas the ratio of other receptors was around 2. 5. We conclude that R1 and R2 are either UV, violet, or blue receptors whereas R3 and R4 are green receptors. Some R6 and R8 are red receptors. We also conclude that the UV secondary peak in the double-peaked green receptor is not simply attributable to the coupling with UV receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00223959
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  • 9
    Electronic Resource
    Electronic Resource
    High resolution measurement of atmospheric carbon dioxide concentration changes by the labial palp organ of the moth Heliothis armigera (Lepidoptera: Noctuidae) (1992)
    Springer
    Journal of comparative physiology 171 (1992), S. 317-324 
    Details
    ISSN: 1432-1351
    Keywords: Carbon dioxide ; Chemoreception ; Lepidoptera ; Microclimate ; Sensory transduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In recordings of single unit action potentials, the responses of CO2-receptors in the labial palp organ of the moth Heliothis armigera to modulation of CO2-density around a background of 350 ppm were investigated. Modulation of CO2-density by square wave changes in concentration at constant barometric pressure evokes modulation of the spike rate. Modulation of CO2-density by square wave changes in barometric pressure at constant CO2-concentration evokes responses similar to those evoked by concentration modulation. For modulation depths of less than 1.5%, the output modulation depth is linearly related to the input; at higher modulation depths the gain decreases progressively. Using sinusoidal pressure modulation, the frequency dependence of both gain and output noise was determined over a range of 0.05 to 12.8 Hz. With increasing frequency the gain progressively increases at a rate of 2.4 dB/octave up to a maximum of 63 at 3 Hz; at higher frequencies, it decreases rapidly. The threshold sensitivity of the receptors, using input noise amplitude density as a criterion, is broadly tuned, with a minimum of 1 % contrast Hz-0.5 between 0.3 and 3 Hz. Using these figures, it is concluded that the sensory organ is capable of detecting fluctuations in CO2-density of 0.14% or 0.5 ppm. The results are related to the fluctuations in CO2-density which occur in a natural environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00223962
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  • 10
    Electronic Resource
    Electronic Resource
    Tangential medulla neurons in the mothManduca sexta. Structure and responses to optomotor stimuli (1993)
    Springer
    Journal of comparative physiology 173 (1993), S. 783-799 
    Details
    ISSN: 1432-1351
    Keywords: Insect vision ; Lepidoptera ; Medulla neurons ; Optomotor stimulation ; Direction selectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract InManduca sexta, large tangential cells connect the medulla via the lobula valley (LoV) tract to the midbrain and the contralateral medulla. Tract neurons have been stained and recorded to determine their responses to optomotor stimulation. Neurons in the LoV-tract comprise a physiologically and anatomically heterogeneous population: 1. Motion insensitive medulla tangential (Mt) neurons arise from cell bodies in the ventral rind. Heterolateral cells arborize massively in both medullae and one or both halves of the midbrain. Mt-neurons respond to changes in light intensity. Physiological and anatomical evidence argues for their monocularity and transmission from the medulla on the side of the soma to the central brain and the contralateral medulla. 2. Motion sensitive neurons with cell bodies behind the protocerebral bridge connect the midbrain to the ipsior contralateral medulla. Direction-selective responses are characterized by excitation to motion in the preferred and inhibition in the opposite direction with maxima either in a horizontal or vertical direction. Peak values appear at contrast frequencies of appr. 3/s. The results suggest that these neurons are binocular and relay information from the midbrain to the medulla. They have been labelled as centrifugal medulla tangential (cMt) neurons. The possible roles for tract neurons in visually guided behaviour are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02451909
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