Showing papers by "University of Konstanz published in 1989"
TL;DR: In this article, the authors investigated the aggregation of three chemically different colloidal systems under both diffusion-limited and reaction-limited aggregation conditions and provided convincing experimental evidence that the two regimes of aggregation are indeed universal.
Abstract: THE aggregation of colloidal particles is of fundamental importance in colloid science and its applications. The recent application of scaling concepts1,2 has resulted in a much deeper understanding of the structure of colloidal aggregates and the kinetics of their formation. Two distinct, limiting regimes of irreversible colloid aggregation have been identified3. Diffusion-limited colloid aggregation occurs when there is negligible repulsive force between the colloidal particles, so that the aggregation rate is limited solely by the time taken for clusters to encounter each other by diffusion. Reaction-limited colloid aggregation occurs when there is still a substantial, but not insurmountable, repulsive force beween the particles, so that the aggregation rate is limited by the time taken for two clusters to overcome this repulsive barrier by thermal activation. These regimes correspond to the limiting cases of rapid and slow colloid aggregation that have long been recognized in colloid science4. An intriguing possibility suggested by recent work is that each of these limiting regimes of colloid aggregation is universal, independent of the chemical details of the particular colloid system. Here we investigate the aggregation of three chemically different colloidal systems under both diffusion-limited and reaction-limited aggregation conditions. A scaling analysis of light-scattering data is used to compare the behaviour and provides convincing experimental evidence that the two regimes of aggregation are indeed universal.
880 citations
TL;DR: This review describes the best studied of Flavoproteins mechanisms and discusses factors possibly governing reactivity and specificity.
Abstract: Flavoproteins are a class of enzymes catalyzing a very broad spectrum of redox processes by different chemical mechanisms. This review describes the best studied of these mechanisms and discusses factors possibly governing reactivity and specificity.
549 citations
TL;DR: In this paper, the seasonal change of the rates of production and emission of methane were determined under in-situ conditions in an Italian rice paddy in 1985 and 1986, by cutting the plants and by trapping emerging gas bubbles with funnels.
Abstract: The seasonal change of the rates of production and emission of methane were determined under in-situ conditions in an Italian rice paddy in 1985 and 1986. The contribution to total emission of CH4 of plant-mediated transport, ebullition, and diffusion through the flooding water was quantified by cutting the plants and by trapping emerging gas bubbles with funnels. Both production and emission of CH4 increased during the season and reached a maximum in August. However, the numbers of methanogenic bacteria did not change. As the rice plants grew and the contribution of plant-mediated CH4 emission increased, the percentage of the produced CH4 which was reoxidized and thus, was not emitted, also increased. At its maximum, about 300 ml CH4 were produced per m2 per hour. However, only about 6% were emitted and this was by about 96% via plant-mediated transport. Radiotracer experiments showed that CH, was produced from H2/CO2. (30–50%) and from acetate. The pool concentration of acetate was in the range of 6–10 mM. The turnover time of acetate was 12–16 h. Part of the acetate pool appeared to be not available for production of CH4 or CO2
484 citations
TL;DR: It is concluded that tumor necrosis factor alpha is likely to act as a final mediator of endotoxin action in a sequence of events which includes formation of leukotriene D4 and reactive oxygen species.
302 citations
TL;DR: It is reported that purified p68 also exhibits RNA-dependent ATPase activity and functions as an RNA helicase in vitro and that T antigen also has an RNA-unwinding activity, which may be involved in the growth-regulating functions of both proteins.
Abstract: It has been proposed that p68, a nuclear protein of relative molecular mass 68,000, functions in the regulation of cell growth and division. A complementary DNA analysis of the protein has revealed extensive amino-acid sequence homology to the products of a set of genes recently identified in organisms as diverse as Escherichia coli and man, which include the eukaryotic translation initiation factor elF-4A. The protein products of the new gene family have several motifs in common which are thought to be involved in nucleic acid unwinding. As yet, however, only elF-4A, through its effect on RNA, has been shown to possess unwinding activity. Here we report that purified p68 also exhibits RNA-dependent ATPase activity and functions as an RNA helicase in vitro. The protein was first identified by its specific immunological cross reaction with the simian virus 40 large T antigen, the transforming protein of a small DNA tumour virus. Surprisingly, T antigen also has an RNA-unwinding activity: the homology between the two polypeptides, although confined to only a small region resembling the epitope of the cross-reacting antibody (PAb204), should therefore be of functional significance. Furthermore, the RNA-unwinding activity may be involved in the growth-regulating functions of both proteins.
284 citations
TL;DR: Reed decline phenomena have been detected in more than 35 lakes in Europe and probable causal factors are grouped into five categories: direct destruction, mechanical damage, grazing, water and sediment quality, lake regulation and related effects.
278 citations
TL;DR: A cage radical mechanism is proposed for both enzymes according to which the initial radical process is terminated through oxidation of carbon-centered radicals by the iron-sulfur catalytic site, followed by ionic rearrangement to PGI2 or TXA2.
276 citations
TL;DR: Circumstantial evidence suggests that type IID fibers are identical with the 2X fibers, previously described by Schiaffino et al. (1986).
Abstract: Combined histochemical and biochemical analyses were performed on rat skeletal muscles in order to determine the myosin heavy chain patterns in specific fiber types. Four myosin heavy chain isoforms were separated by gradient polyacrylamide gel electrophoresis of extracts from single fibers and whole muscle homogenates. Their electrophoretic mobility increased in the order HCIIa, HCIIb, and HCI. HCIIa, HCIIb and HCI were present as unique isoforms in histochemically defined fiber types IIA, IIB and I, respectively. The isoforms HCI and HCIIa coexisted at variable ratios in type IC and IIC fibers. An additional fast myosin heavy chain isoform with an electrophoretic mobility between HCIIa and HCIIb was designated as HCIId because of its abundance in fast fibers of large diameter in the diaphragm. With the exception of slight differences in mATPase staining intensity after acid preincubation, these fibers were almost indistinguishable from type IIB fibers. In view of their specific myosin heavy chain composition (HCIId), these fibers were named type IID. In the extensor digitorum longus muscle, type IID fibers were of smaller size than type IIB and differed from the latter by higher NADH tetrazolium reductase activities. Circumstantial evidence suggests that type IID fibers are identical with the 2X fibers, previously described by Schiaffino et al. (1986).
251 citations
TL;DR: Cultures with H2 as energy source resulted in the enrichment of chemolithotrophic homoacetogenic bacteria whenever incubation temperatures were lower than 20°C, and Hydrogenotrophic methanogens could only be enriched at 30°C from anoxic paddy soil.
Abstract: The effect of temperature on CH4 production, turnover of dissolved H2, and enrichment of H2-utilizing anaerobic bacteria was studied in anoxic paddy soil and sediment of Lake Constance. When anoxic paddy soil was incubated under an atmosphere of H2/CO2, rates of CH4 production increased 25°C, but decreased at temperatures lower than 20°C. Chloroform completely inhibited methano-genesis in anoxic paddy soil and lake sediment, but did not or only partially inhibit the turnover of dissolved H2, especially at low incubation temperatures. Cultures with H2 as energy source resulted in the enrichment of chemolithotrophic homoacetogenic bacteria whenever incubation temperatures were lower than 20°C. Hydrogenotrophic methanogens could only be enriched at 30°C from anoxic paddy soil. A homoacetogen
209 citations
TL;DR: In this article, a distance sensor consisting of a sharply pointed vibrating tip, which is part of a high-Q quartz resonator driven at its resonance frequency, is incorporated into a scanning device.
Abstract: Scanning near-field acoustic microscopy (SNAM) is a new method for imaging the topography of nonconducting surfaces at a potential lateral resolution in the sub-micron range. The basic element of this method is a distance sensor consisting of a sharply pointed vibrating tip, which is part of a high-Q quartz resonator driven at its resonance frequency. The decrease of the resonance frequency or of the amplitude of vibration when an object comes into the proximity of the tip serves as the important signal. The dependence of this signal on pressure and composition of the coupling gas shows that the hydrodynamic forces in the gas are responsible for the coupling between object and tip. The sensor is incorporated into a scanning device. Well-resolved line scans of a grating of 8 μm periodicity, a lateral resolution of 3 μm and a vertical resolution of 5nm have been achieved in our first experiments.
200 citations
TL;DR: Fast-twitch rat muscles contain three fast myosin heavy chains (HC) which can be separated by density gradient gel electrophoresis, and it appears that HCIId is an intermediate form between HCIIb and HCIIa, while single-fiber analyses of normal muscles make it possible to assign these heavy chain isoforms to histochemically defined fiber types IIB, IID, and IIA.
Abstract: Fast-twitch rat muscles contain three fast myosin heavy chains (HC) which can be separated by density gradient gel electrophoresis. Their mobility increases in the order of HCIIa less than HCIId less than HCIIb. In contrast to the rabbit, where chronic low-frequency nerve stimulation induces a fast-to-slow conversion, stimulation for up to 56 days does not lead to appreciable increases in the relative concentration of the slow myosin heavy chain HCI in rat fast-twitch muscles. However, chronic stimulation of rat fast-twitch muscle does evoke a rearrangement of the fast myosin heavy chain isoform pattern with a progressive decrease in HCIIb and progressive increases in HCIIa and HCIId. As judged from the time course and extent of these transitions, it appears that HCIId is an intermediate form between HCIIb and HCIIa. Single-fiber analyses of normal muscles make it possible to assign these heavy chain isoforms to histochemically defined fiber types IIB, IID, and IIA. The stimulation-induced fiber transformations produce numerous hybrid fibers displaying more than one myosin heavy chain isoform. Some transforming fibers contain up to four different myosin heavy chain isoforms.
TL;DR: A new, rod-shaped, Gram-negative, non-sporing sulfate reducer was enriched and isolated from marine sediment with aniline as sole electron donor and carbon source and degraded anilines completely to CO2 and NH3 with stoichiometric reduction of sulfate to sulfide.
Abstract: A new, rod-shaped, Gram-negative, non-sporing sulfate reducer (strain Ani1) was enriched and isolated from marine sediment with aniline as sole electron donor and carbon source. The strain degraded aniline completely to CO2 and NH3 with stoichiometric reduction of sulfate to sulfide. Strain Ani1 also degraded aminobenzoates and further aromatic and aliphatic compounds. The strain grew in sulfide-reduced mineral medium supplemented only with vitamin B12 and thiamine. Cells contained cytochromes, carbon monoxide dehydrogenase, and sulfite reductase P 582, but no desulfoviridin. Strain Ani1 is described as a new species of the genus Desulfobacterium, D. anilini. Marine enrichments with the three dihydroxybenzene isomers led to three different strains of sulfate-reducing bacteria; each of them could grow only with the isomer used for enrichment. Two strains isolated with catechol (strain Cat2) or resorcinol (strain Re10) were studied in detail. Both strains oxidized their substrates completely to CO2 and contained cytochromes, carbon monoxide dehydrogenase, and sulfite reductase P 582. Desulfoviridin was not present. Whereas the rod-shaped catechol oxidizer (strain Cat2) was able to grow on 18 aromatic compounds and several aliphatic substrates, the coccoid resorcinol-degrading bacterium (strain Re10) utilized only resorcinol, 2,4-dihydroxybenzoate and 1,3-cyclohexanedion. These strains could not be affiliated with existing species of sulfate-reducing bacteria. A further coccoid sulfate-reducing bacterium (strain Hy5) was isolated with hydroquinone and identified as a subspecies of Desulfococcus multivorans. Most-probable-number enumerations with catechol, phenol, and resorcinol showed relatively large numbers (104–106 per ml) or aryl compound-degrading sulfate reducers in marine sediment samples.
TL;DR: This divergence was progressive and was interpreted to indicate that the increase in cytochrome-c-oxidase content was brought about not only by changes in the levels of the specific mRNAs, but also by alterations at the level of translation.
Abstract: Fast-twitch tibialis anterior muscle of the rat was subjected to chronic low-frequency (10 Hz, 10 h daily) nerve stimulation in order to investigate the time course of changes in cytochrome-c-oxidase activity, as well as in tissue levels of specific mitochondrially and nuclear-encoded, cytochrome-c-oxidase-subunit mRNAs. Chronic stimulation induced a progressive increase in cytochrome-c-oxidase activity which was threefold elevated after 35 days. A similar increase was recorded for citrate-synthase activity. Glyceraldehyde-3-phosphate dehydrogenase, which was studied as a glycolytic reference enzyme, moderately decreased, as did the tissue level of its corresponding mRNA. There was a parallel increase in the tissue levels of the two cytochrome-c-oxidase-subunit mRNAs over the entire stimulation time course. The extent of increase (stimulated/control) was 2.4 +/- 0.3 and 1.8 +/- 0.2 (means +/- SEM) for the mitochondrial and nuclear subunit mRNAs, respectively. This parallel increase suggested a coordinate regulation of the two subunits. The increase in cytochrome-c-oxidase activity initially corresponded to the changes at the mRNA level. However, with longer stimulation times (beyond 14 days), the increase in cytochrome-c-oxidase activity clearly exceeded that of the two mRNAs. This divergence was progressive and was interpreted to indicate that the increase in cytochrome-c-oxidase content was brought about not only by changes in the levels of the specific mRNAs, but also by alterations at the level of translation.
TL;DR: In this paper, the shape of the master curve of colloid aggregates is predicted for different cluster distributions for two limiting regimes, diffusion-limited and reaction-limited colloid aggregation, using data from several completely differient colloids.
Abstract: Fractal colloid aggregates are studied with both static and dynamic light scattering. The dynamic light scattering data are scaled onto a single master curve, whose shape is sensitive to the structure of the aggregates and their mass distribution. By using the structure factor determined from computer-simulated aggregates, and including the effects of rotational diffusion, we predict the shape of the master curve for different cluster distributions. Excellent agreement is found between our predictions and the data for the two limiting regimes, diffusion-limited and reaction-limited colloid aggregation. Furthermore, using data from several completely differient colloids, we find that the shapes of the master curves are identical for each regime. In addition, the cluster fractal dimensions and the aggregation kinetics are identical in each regime. This provides convincing experimental evidence of the universality of these two regimes of colloid aggregation.
TL;DR: Reductive (dithionite) and oxidative (ferricyanide) titrations showed that the conversion of the purple form I to the blue species III was fully reversible in the absence of dioxygen, similar to earlier observations for the regenerated, catalytically inactive protein.
Abstract: The oxidation-reduction and spectroscopic properties of various forms of nitrous oxide reductase from Pseudomonas stutzeri were investigated. The high-activity form I of the enzyme (purple, 8 Cu, Mr 140,000) was reduced by a large variety of cationic, anionic and photochemically generated agents. The blue form III was the only product found in these experiments under anaerobic conditions. Reductive (dithionite) and oxidative (ferricyanide) titrations showed that the conversion of the purple form I to the blue species III was fully reversible in the absence of dioxygen. Two kinetically different phases of the reaction of form I with a stoichiometric amount of dithionite (1e- -equivalent/Cu) were detected: in the fast phase (seconds), the purple chromophore with lamba max at 540 nm disappeared almost completely, whereas in the slower phase (minutes) the blue species with lambda max around 650 nm was generated. Irrespective of the nature of the reductant the blue species did not react even at large excess of reductant. It was reoxidized by ferricyanide, hydrogen peroxide and nitric oxide. A new, catalytically inactive derivative of nitrous oxide reductase (form V, 2 Cu, Mr 140,000) was isolated from a transposon Tn5-induced mutant with defective chromophore biosynthesis. The pink color of the mutant protein faded almost completely after addition of 0.5e- -equivalent/Cu. In this case no blue species was found, similar to earlier observations for the regenerated, catalytically inactive protein. Varying with the sample and the pH, 50-80% of the total copper of form I was in an electron-paramagnetic-resonance-(EPR)-silent state as compared to 47% in the mutant protein. The broad, featureless EPR signal recorded at 9.32 GHz for the blue, reduced form III of nitrous oxide reductase represented approximately 20% of the total copper. For the blue species no resolution enhancement was achieved at 34 GHz. At this frequency both forms I and V showed similar EPR signals with apparent g-values at 2.16 and 1.99. At 9.32 GHz, form V had an EPR signal with gII at 2.18, AII = 3.55 mT (4 or 5 lines, in contrast to form I) and gI at 2.03. Above 100 K the splitting of the gII region into seven equidistant lines in the EPR signal of the high-activity form I and the hyperfine structure of the perpendicular transition disappeared. Carbon monoxide and nitric oxide, but not nitrous oxide, had marked effects on the spectroscopic properties of the purple form I. Marked effects were also obtained for the exogenous ligands nitrite, azide, cyanate and thiocyanate.(ABSTRACT TRUNCATED AT 400 WORDS)
TL;DR: It is observed that the location of the kinases relative to the membrane components in the contact fraction resembled that of intact mitochondria, which suggested an important role of the voltage dependence of the outer membrane pore in anion exchange.
TL;DR: In this paper, the formation of racemic and meso diastereomers of disubstituted ansa-zirconocenes (CH3)2Si(1-C5H3-3-R)2ZrCl2 (R t-butyl, trimethylsilyl, α,α-dimethylbenzyl and 1-phenylcyclohexyl) from dimethylsilanediyl-bridged, symmetrically substituted bis-cyclopentadienyl dianion derivatives and
TL;DR: In this paper, the concavity of the likelihood function is proved by means of an inequality involving the trigamma function, and the computation of maximum likelihood estimates is discussed.
Abstract: Global concavity of the likelihood function is proved by means of an inequality involving the trigamma function. The computation of maximum likelihood estimates is discussed.
TL;DR: It is proposed that during thiosulfate and sulfite disproportionation sulfate is formed via APS reductase and ATP sulfurylase, but not by sulfite oxidoreductase.
Abstract: Disproportionation of thiosulfate or sulfite to sulfate plus sulfide was found in several sulfate-reducing bacteria. Out of nineteen strains tested, eight disproportionated thiosulfate, and four sulfite. Growth with thiosulfate or sulfite as the sole energy source was obtained with three strains (Desulfovibrio sulfodismutans and the strains Bra02 and NTA3); additionally, D. desulfuricans strain CSN grew with sulfite but not with thiosulfate, although thiosulfate was disproportionated. Two sulfur-reducing bacteria, four phototrophic sulfur-oxidizing bacteria (incubated in the dark), and Thiobacillus denitrificans did not disproportionate thiosulfate or sulfite. Desulfovibrio sulfodismutans and D. desulfuricans CSN formed sulfate from thiosulfate or sulfite even when simultaneously oxidizing hydrogen or ethanol, or in the presence of 50 mM sulfate. The capacities of sulfate reduction and of thiosulfate and sulfite disproportionation were constitutively present. Enzyme activities required for sulfate reduction (ATP sulfurylase, pyrophosphatase, APS reductase, sulfite reductase, thiosulfate reductase, as well as adenylate kinase and hydrogenase) were detected in sufficient activities to account for the growth rates observed. ADP sulfurylase and sulfite oxidoreductase activities were not detected. Disproportionation was sensitive to the uncoupler carbonylcyanide m-chlorophenylhydrazone (CCCP) but not to the ATPase inhibitor dicyclohexylcarbodiimide (DCCD). It is proposed that during thiosulfate and sulfite disproportionation sulfate is formed via APS reductase and ATP sulfurylase, but not by sulfite oxidoreductase. Reversed electron transport must be assumed to explain the reduction of thiosulfate and sulfite by the electrons derived from APS reductase.
TL;DR: Muon spin rotation experiments performed on superconducting samples clearly show that internal magnetic fields coexist at low temperatures with superconductivity forx\ensuremath{\le}0.15$.
Abstract: Muon spin rotation experiments performed on superconducting ${\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}\mathrm{Cu}{\mathrm{O}}_{4}$ samples clearly show that internal magnetic fields coexist at low temperatures ($Tl2$ K) with superconductivity for $x\ensuremath{\le}0.15$. The magnetic fields in the superconducting state are an order of magnitude smaller than the corresponding fields in undoped ${\mathrm{La}}_{2}$Cu${\mathrm{O}}_{4}$. The data are discussed in the context of a magnetic pairing mechanism in high-${T}_{c}$ superconductors.
TL;DR: In this paper, a simple model of simultaneous NO production and NO uptake was proposed and the dependence of net NO fluxes on gas flow rates and on NO mixing ratios could be described by using this model, rates of gross NO production, rate constants of NO uptake, and NO compensation mixing ratios were determined as function of the soil type and the incubation condition.
Abstract: Fluxes of NO from three different soils have been studied by a flow-through system in the laboratory as a function of gas flow rate, of NO mixing ratio, and of incubation conditions. The dependence of net NO fluxes on gas flow rates and on NO mixing ratios could be described by a simple model of simultaneous NO production and NO uptake. By using this model, rates of gross NO production, rate constants of NO uptake, and NO compensation mixing ratios could be determined as function of the soil type and the incubation condition. Gross NO production rates were one to two orders of magnitude larger under anaerobic than under aerobic conditions. NO uptake rate constants, on the other hand, were only 5–8 times larger so that the compensation mixing ratios of NO were in a range of about 1600–2200 ppbv under anaerobic and of about 50–600 ppbv under aerobic conditions. The different soils exhibited similar NO uptake rate constants, but the gross NO production rate and compensation mixing ratio was significantly higher in an acidic (pH 4.7) sandy clay loam than in other less acidic soils. Experiments with autoclaved soil samples showed that both NO production and NO uptake was mainly due to microbial metabolism.
TL;DR: Large T antigen, the regulatory protein encoded by simian virus 40, has DNA helicase activity and unwinds double-stranded DNA at the expense of ATP, and it appears that the bound nucleotide determines whether T antigen acts as an RNA helicase or as aDNA helicase.
TL;DR: It is suggested that environmentally induced changes in DNA supercoiling may play a role in determining the level of porin expression, and these findings have implications for current models of Porin regulation.
Abstract: The OmpC and OmpF porins are major outer membrane proteins of Escherichia coli and Salmonella typhimurium. Their expression is affected by many environmental factors and by mutations in a variety of independent genes. The pair of regulatory proteins, OmpR and EnvZ, are required for normal porin expression. Despite intensive investigation, the mechanisms by which porin expression is regulated remain unclear. Mutations which alter supercoiling, as well as inhibitors of DNA gyrase, show that porin expression is extremely and specifically sensitive to the level of DNA supercoiling. Our data lead us to suggest that environmentally induced changes in DNA supercoiling may play a role in determining the level of porin expression. These findings have implications for current models of porin regulation.
TL;DR: In this paper, the authors found that the contribution of MBA to H2-dependent methanogenesis and turnover of dissolved H2 did not change significantly for up to 7 months of incubation.
Abstract: Interspecies H2 transfer within methanogenic bacterial associations (MBA) accounted for 95–97% of the conversion of 14CO2 to 14CH4 in anoxic paddy soil. Only 3–5% of the 14CH4 were produced from the turnover of dissolved H2. The H2-syntrophic MBA developed within 5 days after the paddy soil had been submerged and placed under anoxic atmosphere. Afterwards, both the contribution of MBA to H2-dependent methanogenesis and the turnover of dissolved H2 did not change significantly for up to 7 months of incubation. However, while the rates of H2-dependent methanogenesis stayed relatively constant, the rates of total methanogenesis decreased. The contribution of MBA to H2-dependent methanogenesis was further enhanced to 99% when the temperature was shifted from 30°C to 17°C, or when the soil had been planted with rice. This enhancement was partially due to an increased utilization of dissolved H2 by chloroform-insensitive non-methanogenic bacteria, most probably homoacetogens, so that CH4 production was almost completely restricted to H2-syntrophic MBA. The activity of MBA, as measured by the conversion of 14CO2 to 14CH4, was stimulated by glucose, lactate, and ethanol to a similar or greater extent than by exogenous H2. Propionate and acetate had no effect.
TL;DR: This study investigated whether for females, who are said to be less strongly lateralized for cognitive functions than men, hemispheric superiority might depend on the phase of the menstrual cycle, and found that asymmetry in face perception decreased linearly from a large right hemisphere superiority during menstruation to a small left Hemisphere superiority during the premenstrual phase.
TL;DR: The data suggest that the SA channel is responsible for the mechanotransduction process in the stretch receptor neuron of the crayfish Orconectes limosus.
Abstract: Single stretch-activated ion channels were studied on the soma and primary dendrites of stretch receptor neurons of the crayfish Orconectes limosus. When the membrane of the patch was deformed by applying suction to the pipette, a marked nonlinear increase in single-channel activity could be observed in two types of channels. These were indistinguishable on the basis of their single-channel conductances but differed in their voltage range of activation. One type showed strong inward rectification (RSA channel) and the second type was largely voltage independent (SA channel). A linear relationship was found between negative pressure and the natural logarithm of the channels' open probability. For an e-fold change in pressure, the average sensitivity was 8.7 +/- 0.4 (SD, n = 5) mmHg for the RSA channel and 5.6 +/- 2.2 (n = 5) mmHg for the SA channel. Both channels were found to be permeable to mono- and divalent cations. Current-voltage relationships were linear with slope conductances for the SA channel of: 71 +/- 11 (SD, n = 3) pS for K+, 50 +/- 7.4 (n = 5) pS for Na+, and 23 pS for Ca++. Similar values were found for the RSA channel. The data suggest that the SA channel is responsible for the mechanotransduction process in the stretch receptor neuron.
TL;DR: In both years, prostome nanociliates dominated numerically, while strobiliids in the size range 20–35μm contributed most significantly to ciliate production.
Abstract: Abundance, biovolume, and species composition of pelagic ciliates in Lake Constance were recorded over two annual cycles (1987/88). Production was estimated from mean annual biovolumes and size-specific growth rates obtained from the literature. Cell concentrations and biovolumes ranged from 0.1 to 120 cells ml−1 and from 3 to 1,200 mm3 m−3, respectively. Mean annual values were, respectively, 6.8 cells ml−1 and 94 mm3 m−3 in 1987, and 12.0 cells ml−1 and 130 mm3 m−3 in 1988. In both years, prostome nanociliates (<20μm) dominated numerically, while strobiliids in the size range 20–35μm contributed most significantly to ciliate production. Ciliate community production, according to a crude calculation, yielded approximately 10–15 g C m−2 year−1.
TL;DR: Differences in sensitivity were found, however, at shorter wavelengths, with the yellow field being more sensitive than the red at wavelengths below 500 nm and especially in the ultraviolet spectral range.
Abstract: The spectral sensitivity of the red and the yellow retinal fields of head-fixed pigeons was separately measured for wavelengths between 340 and 640 nm by a behavioral perimetric technique. Within this spectral range the mean spectral sensitivity of both fields was found to be maximal at 584 nm and minimal at the lower ultraviolet wavelengths. Differences in sensitivity were found, however, at shorter wavelengths, with the yellow field being more sensitive than the red at wavelengths below 500 nm and especially in the ultraviolet spectral range. These sensitivity differences are discussed in relation to other functional differences between the pigeon's retinal fields.
TL;DR: In this paper, the formation of molecule-like complexes, consisting of a defect and a radioactive 111In atom, is studied using the perturbedγγ angular correlation technique (PAC), where the complexes are characterized by their defect specific electric field gradients which also contain information on the geometry of the formed complexes.
Abstract: The formation of molecule-like complexes, consisting of a defect and a radioactive111In atom, is studied using the perturbedγγ angular correlation technique (PAC). The complexes are characterized by their defect specific electric field gradients which also contain information on the geometry of the formed complexes. Whereas the complex is formed with the111In atom, its electric field gradient is measured after the decay of the radioactive111In atom to111Cd. Formation and dissolution of the molecule-like complexes is pursued for a variety of different conditions, such as sample temperature, dopant concentration and position of the Fermi level. In particular, the interaction of In atoms with the following defects in Si was investigated: Intrinsic defects, created by particle irradiation; substitutional donor atoms (P, As, Sb, Bi); and interstitial impurity atoms (Li, H, and an unidentified X defect); especially, the latter ones are known to passivate acceptor atoms in Si. Methodology and specific properties of the PAC technique will be illustrated with the help of these examples.
TL;DR: The results indicated that probably both, ΔpH and ΔΨ drive sulfate accumulation and that sulfate is taken up electrogenically in symport with more than 2 protons, and not in favour of an ATP-dependent transport system.
Abstract: Uptake of 35S-labelled sulfate was studied with a new isolate of Desulfovibrio desulfuricans, strain CSN. Micromolar additions of sulfate (1–10 μM or nmol/mg protein) to cell suspensions incubated in 150 mM KCl at-1°C were almost completely taken up and accumulated about 5,000-fold. Accumulation was not influenced by incubation in NaCl instead of KCl, by acidic pH (5.5) or by incubation under air for 10 min. In alkaline milieu (pH 8.5), after prolonged contact with air (2 h), or after growth with excess sulfate or thiosulfate as electron acceptor, the amount taken up was diminished approximately by half. Pasteurization inhibited sulfate uptake completely. With increasing concentrations of added sulfate (0.1 to 2.5 mM) the intracellular concentration increased only slowly up to 25 mM, and the accumulation factor decreased down to 8. Sulfate transport was reversible. Accumulated sulfate was rapidly lost from the cells after addition of excess non-labelled sulfate or after addition of the uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP). The ATPase inhibitor dicyclohexylcarbodiimide (DCCD) specifically inhibited sulfate reduction but had no immediate influence on sulfate accumulation. Addition of the phosphate analogue arsenate (5 mM) was without effect. These results were not in favour of an ATP-dependent transport system. The K+-H+-antiporter nigericin (in 150 mM KCl) and the Na+-H+-antiporter monensin (in 150 mM NaCl) caused partial inhibition of sulfate accumulation, whereas the K+-transporter valinomycin (in 150 mM KCl) and the Na+-H+ exchange inhibitor amiloride (2 mM) were without effect. The permeant thiocyanate anion (150 mM) inhibited sulfate uptake by 60% at pH 7, and completely at pH 8.5. Although the effects of the different ionophores on the chemiosmotic gradients have not been studied so far, the results indicated that probably both, ΔpH and ΔΨ drive sulfate accumulation and that sulfate is taken up electrogenically in symport with more than 2 protons. The structural sulfate analogues tungstate and molybdate (0.1 mM, each) did not affect sulfate accumulation, although molybdate inhibited sulfate reduction. Chromate completely blocked both of these activities. Sulfite and selenite caused little or no decrease of sulfate accumulation, whereas with thiosulfate and selenate significant inhibition was observed.