Showing papers by "Academy of Sciences of the Czech Republic published in 1994"
TL;DR: In this article, a model based on the assumption of plug flow of supercritical solvent through a fixed bed of milled material was developed for both extraction periods and a new model with analytical solution was developed on the basis of these models.
553 citations
TL;DR: In this paper, the authors investigated the effect of milling of grape seeds, solvent flow rate and flow direction on the course of extraction and found that the smaller the amount of milled seeds in the extractor and the slower the upward flow, the more pronounced was this effect.
309 citations
TL;DR: A new method is described for automatic control point selection and matching that can produce subpixel registration accuracy and is demonstrated by registration of SPOT and Landsat TM images.
Abstract: A new method is described for automatic control point selection and matching. First, reference and sensed images are segmented and closed-boundary regions are extracted. Each region is represented by a set of affine-invariant moment-based features. Correspondence between the regions is then established by a two-stage matching algorithm that works both in the feature space and in the image space. Centers of gravity of corresponding regions are used as control points. A practical use of the proposed method is demonstrated by registration of SPOT and Landsat TM images. It is shown that the authors' method can produce subpixel registration accuracy. >
292 citations
TL;DR: In this paper, a perturbed virial expansion with a theoretically defined temperature-dependent reference hard sphere term is proposed to guarantee the thermodynamic consistency of the pressure and internal energy of the Lennard-Jones fluid.
276 citations
TL;DR: NK-resistant tumour cells are rendered susceptible by preincubation with liposomes expressing NKR-P1 ligands, suggesting that purging of tumour or virally infected cells in vivo may be a therapeutic possibility.
Abstract: THIS PAPER HAS BEEN RETRACTED; see retraction
. A diversity of high-affinity Oligosaccharide ligands are identified for NKR-P1, a membrane protein on natural killer (NK) cells which contains an extracellular Ca2+-dependent lectin domain. Interactions of such oligosaccharides on the target cell surface with NKR-P1 on the killer cell surface are crucial both for target cell recognition and for delivery of stimulatory or inhibitory signals linked to the NK cytolytic machinery. NK-resistant tumour cells are rendered susceptible by preincubation with liposomes expressing NKR-P1 ligands, suggesting that purging of tumour or virally infected cells in vivo may be a therapeutic possibility.
253 citations
TL;DR: The ability to time the response sequence in such a way that the response 5 were placed right ahead of the stimuli started to break clown, i.e., the task was fulfilled by reactions to the stimuli rather than by advanced responses.
Abstract: The concept of a temporal integration process in the timing mechanisms in the brain, postulated on the basis of experimental observations from various paradigms (for a review see P$oUppel, 1978), has been explored in a sensorimotor synchronization task. Subjects synchronized their finger taps to sequences of auditory stimuli with interstimulus-onset intervals (ISIs) between 300 and 4800 msec in different trials. Each tonal sequence consisted of 110 stimuli; the tones had a frequency of 500 Hz and a duration of 100 msec. As observed previously, response onsets preceded onsets of the stimuli by some tens of milliseconcls for ISIs in the range from about 600 to 1800 msec. For ISIs longer than or equal to 2400 msec, the ability to time the response sequence in such a way that the response 5 were placed right ahead of the stimuli started to break clown, i.e., the task was fulfilled by reactions to the stimuli rather than by advanced responses. This observation can he understood within the general framework of a temporal integration puce 55 that is supposed to have a maximal capacity (integration interval) of approximately 3 sec. Only if successive stimuli fall within one integration period, can motor programs be initiated properly by a prior stimulus and thus lead to an appropriate synchronization between the stimulus sequence and corresponding motor acts.
228 citations
TL;DR: After dispersing the granular component and the dense fibrillar component by a hypotonic treatment, removal of most chromatin and preparation of resinless sections, fibrillsar centres remained fixed to a nucleoskeleton and are incorporated into a model for rRNA transcription.
Abstract: Sites of transcription of ribosomal RNA in HeLa cells were visualized by electron microscopy. Cells were either incubated with Br-uridine, or permeabilized and then incubated with BrUTP, before sites containing Br-RNA were immunolabeled with gold particles. Short incubations ensured that most incorporated analogue remained at synthetic sites. Fibrillar centres were unlabelled except at their periphery; label was concentrated over certain regions of the surrounding dense fibrillar component. These results suggest that the dense fibrillar component is the site of rRNA transcription. After dispersing the granular component and the dense fibrillar component by a hypotonic treatment, removal of most chromatin and preparation of resinless sections, fibrillar centres remained fixed to a nucleoskeleton. These structural and functional features are incorporated into a model for rRNA transcription.
212 citations
TL;DR: The dominant presence of POD and Mn-dependent peroxidase in extracts from degraded wood suggest a cooperative role of the two enzymes during white rot decay by the test fungi.
Abstract: The production of the H(2)O(2)-generating enzyme pyranose oxidase (POD) (EC 1.1.3.10) (synonym, glucose 2-oxidase), two ligninolytic peroxidases, and laccase in wood decayed by three white rot fungi was investigated by correlated biochemical, immunological, and transmission electron microscopic techniques. Enzyme activities were assayed in extracts from decayed birch wood blocks obtained by a novel extraction procedure. With the coupled peroxidase-chromogen (3-dimethylaminobenzoic acid plus 3-methyl-2-benzothiazolinone hydrazone hydrochloride) spectrophotometric assay, the highest POD activities were detected in wood blocks degraded for 4 months and were for Phanerochaete chrysosporium (149 mU g [dry weight] of decayed wood), Trametes versicolor (45 mU g), and Oudemansiella mucida (1.2 mU g), corresponding to wood dry weight losses of 74, 58, and 13%, respectively. Mn-dependent peroxidase activities in the same extracts were comparable to those of POD, while lignin peroxidase activity was below the detection limit for all fungi with the veratryl alcohol assay. Laccase activity was high with T. versicolor (422 mU g after 4 months), in trace levels with O. mucida, and undetectable in P. chrysosporium extracts. Evidence for C-2 specificity of POD was shown by thin-layer chromatography detection of 2-keto-d-glucose as the reaction product. By transmission electron microscopy-immunocytochemistry, POD was found to be preferentially localized in the hyphal periplasmic space of P. chrysosporium and O. mucida and associated with membranous materials in hyphae growing within the cell lumina or cell walls of partially and highly degraded birch fibers. An extracellular distribution of POD associated with slime coating wood cell walls was also noted. The periplasmic distribution in hyphae and extracellular location of POD are consistent with the reported ultrastructural distribution of H(2)O(2)-dependent Mn-dependent peroxidases. This fact and the dominant presence of POD and Mn-dependent peroxidase in extracts from degraded wood suggest a cooperative role of the two enzymes during white rot decay by the test fungi.
198 citations
TL;DR: Coprecipitation and preclearing experiments indicate the existence of large multicomponent complexes containing jointly the seven components, although some “incomplete” complexes lacking some of the components may also exist.
Abstract: Four of the tetraspans family antigens expressed in B cells, CD37, CD53, TAPA-1, and R2/C33, as well as at least two other molecules, CD19 and CD21, coprecipitate with DR antigens from mild detergent lysates of human B-cell lines and tonsillar B cells. Coprecipitation and preclearing experiments indicate the existence of large multicomponent complexes containing jointly the seven components, although some "incomplete" complexes lacking some of the components may also exist. The complexes contain only a relatively small fraction of the total cellular pool of relevant molecules. The existence of these "tetraspans-DR complexes" may be related to the previously reported antiproliferative and signaling effects of antibodies against most of their components.
178 citations
TL;DR: These data represent the first detailed in vivo measurements of diffusion parameters α, λ, and k‘ during and after progressive ischemia and anoxia, which could affect the diffusion and aggravate the accumulation of ions, neurotransmitters, metabolic substances, and drugs used in therapy of nervous diseases.
Abstract: Extracellular space (ECS) volume fraction (alpha), ECS tortuosity (lambda), and nonspecific uptake (k'), three parameters affecting the diffusion of substances in nervous tissue, were studied during ischemia and anoxia in the rat spinal cord gray matter in vivo. Progressive ischemia evoked by exsanguination, as well as anoxia evoked by respiratory or cardiac arrest, produced prominent extracellular K+ and pH changes closely related to a decrease in blood pressure and amplitude of field potentials. With use of ion-selective microelectrodes, the changes in the diffusion parameters were measured by quantitative analysis of concentration-time profiles of tetramethylammonium (TMA+) applied by iontophoresis concomitantly with ionic shifts. Under normoxic conditions (in rats with blood pressure of 80-110 mm Hg) diffusion parameters in the dorsal horn gray matter at depth 500-900 microns were as follows: alpha = 0.20 +/- 0.019, lambda = 1.62 +/- 0.12, k' = 4.6 +/- 2.5 x 10(-3) s-1 (mean +/- SD, n = 39). Extracellular K+, pH, and diffusion properties gradually changed during progressive ischemia. As the blood pressure fell to 50-60 mm Hg and field potential amplitude to 20-60%, K+ rose to 6-12 mM, pHe fell by approximately 0.05-0.1 pH unit, and volume fraction of the ECS significantly decreased, to alpha = 0.16 +/- 0.019 (n = 22). Even though the tortuosity remained virtually constant, the nonspecific uptake significantly decreased to k' = 3.4 +/- 1.8 x 10(-3) s-1. As the blood pressure fell to 20-30 mm Hg and field potential amplitude to 0-6%, K+ rose to 60-70 mM, pHe fell by approximately 0.6-0.8 pH unit, and all three diffusion parameters significantly changed. The ECS volume fraction decreased to alpha = 0.05 +/- 0.021, tortuosity increased to lambda = 2.00 +/- 0.24, and TMA+ uptake decreased to k' = 1.5 +/- 1.6 x 10(-3) s-1 (n = 12). No further increase in extracellular K+ or changes in the alpha were found during and up to 120 min after the death of the animal. However, there was a further significant increase in lambda = 2.20 +/- 0.14 and decrease in k' = 0.4 +/- 0.3 x 10(-3) s-1 (n = 24). The acid shift reached its maximum level at approximately 5-10 min after respiratory arrest and then the pHe gradually increased by approximately 0.2 unit. Full recovery to "normoxic" diffusion parameters was achieved after reinjection of the blood or after an injection of noradrenaline during severe ischemia, if this resulted in a rise in blood pressure above 80 mm Hg and a decrease in extracellular K+ below 12 mM.(ABSTRACT TRUNCATED AT 400 WORDS)
167 citations
TL;DR: Treatment of mice with doxorubicin-HPMA copolymer conjugate achieved treated/control lifespans up to 320% compared with only 133% using aggressive regimens of free doxorbicin (3 x 5 mg kg-1), and HPMACopolymers bearing fluorescein isothiocyanate accumulated in vascularised stromal regions, particularly in new growth sites at the tumour periphery.
Abstract: Doxorubicin (5 mg kg-1) was administered intravenously to C57 mice bearing subcutaneous B16F10 melanomas, distributing into the tumour with an area under the concentration-time curve (0-48 h; AUC) of 8.7 micrograms h g-1. Injection of doxorubicin-N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer conjugate, containing 5 mg of doxorubicin equivalent per kg, mediated an AUC for free doxorubicin (i.e. doxorubicin released from the conjugate) of 15.2 micrograms h g-1 and for total doxorubicin (i.e. free plus conjugated) of 149.1 micrograms h g-1. An increased dose of doxorubicin-HPMA copolymer conjugate (18 mg of doxorubicin equivalent per kg) produced AUC values of 40.1 micrograms h g-1 and 671.7 micrograms h g-1 for free and total doxorubicin respectively. Hence administration of doxorubicin-HPMA copolymer conjugate achieved rises of 1.7- to 4.6-fold in tumour AUC (free doxorubicin) and 17.19 to 77.0-fold in tumour AUC (total doxorubicin). HPMA copolymers bearing fluorescein isothiocyanate accumulated in vascularised stromal regions, particularly in new growth sites at the tumour periphery. Treatment of mice with doxorubicin-HPMA copolymer conjugate achieved treated/control lifespans up to 320% (three doses of 27 mg of doxorubicin equivalent per kg) compared with only 133% using aggressive regimens of free doxorubicin (3 x 5 mg kg-1).
TL;DR: The genetic control of sex determination from a number of plant species is reviewed to illustrate the variety of extant mechanisms and species that are now used as models to investigate the molecular biology ofsex determination are emphasized.
Abstract: Most flowering plant species are hermaphroditic, but a small number of species in most plant families are unisexual (i.e., an individ-ual will produce only male or female gametes). Because species with unisexual flowers have evolved repeatedly from hermaphroditic progenitors, the mechanisms controlling sex determination in flowering plants are extremely diverse. Sex is most strongly determined by genotype in all species but the mechanisms range from a single controlling locus to sex chromosomes bearing several linked locirequired for sex determination. Plant hormones also influence sex expression with variable effects from species to species. Here, we review the genetic control of sex determination from a number of plant species to illustrate the variety of extant mechanisms. We emphasize species that are now used as models to investigate the molecular biology of sex determination. We also present our own investigations of the structure of plant sex chromosomes of white campion (Silene latifolia - Melan-drium album). The cytogenetic basis of sex determination in white campion is similar to mammals in that it has a male-specific Y-chromosome that carries dominant male determining genes. If one copy of this chromosome is in the genome, the plant is male. Otherwise it is female. Like mammalian Y-chromosomes, the white campion Y-chromosome is rich in repetitive DNA. We isolated repetitive sequences from microdissected Y-chromosomes of white campion to study the distribution of homologous repeated sequences on the Y-chromosome and the other chromosomes. We found the Y to be especially rich in repetitive sequences that were generally dispersed over all the white campion chromosomes. Despite its repetitive character, the Y-chromosome is mainly euchromatic. This may be due to the relatively recent evolution of the white campion sex chromosomes compared to the sex chromosomes of animals. © 1994 Wiley-Liss, Inc.
TL;DR: In this article, an exact linear integral relation between the Fukui functions of insulators or molecules and the probability density of the frontier orbitals of Kohn-Sham theory was obtained.
Abstract: The local softness and the Fukui function emerge from density functional theory as measures of local electronic reactivity. We obtain here an exact linear integral relation between the Fukui functions of insulators or molecules and the probability density of the frontier orbitals of Kohn–Sham theory. The same linear map holds between the local softness and the local Kohn–Sham density of states at the Fermi level for metals. The kernel in those relations is the inverse of the transpose of the potential response function (PRF) of Kohn–Sham theory. The PRF has the form of the static Hartree dielectric function with an exchange and correlation interaction added to the bare Coulomb interaction. The exact static dielectric function also has the Hartree form, but with a renormalized polarization propagator. The map is norm preserving for systems with energy gaps such as insulators and molecules and norm reducing or screening for systems with a finite density of states above the ground state such as normal metals...
TL;DR: In this paper, the H1 detector at HERA was used for a class of deep inelastic electron-proton scattering (DIS) events (5 < Q2 < 120 GeV2) at low Bjorken-x (10−4 < x < 10−2) which have almost no hadronic energy flow in a large interval of pseudo-rapidity around the proton remnant direction and which cannot be attributed to our present understanding of DIS and fluctuations in final state hadronic fragmentation.
TL;DR: In this article, the authors extended the meaning of chemical threshold to such chemical compositions and bonding arrangement (even for the case R < 1) where the energy of formation reaches the most negative value.
TL;DR: The two HMG-box domains of HMG1 are capable of manipulating DNA by looping, compaction and changes in topology by modulation of the DNA-binding properties, and the acidic C-tail down-regulates these effects by modulationof DNA- binding properties.
Abstract: We have compared HMG1 with the product of tryptic removal of its acidic C-terminal domain termed HMG3, which contains two 'HMG-box' DNA-binding domains. (i) HMG3 has a higher affinity for DNA than HMG1. (ii) Both HMG1 and HMG3 supercoil circular DNA in the presence of topoisomerase I. Supercoiling by HMG3 is the same at approximately 50 mM and approximately 150 mM ionic strength, as is its affinity for DNA, whereas supercoiling by HMG1 is less at 150 mM than at 50 mM ionic strength although its affinity for DNA is unchanged, showing that the acidic C-terminal tail represses supercoiling at the higher ionic strength. (iii) Electron microscopy shows that HMG3 at a low protein:DNA input ratio (1:1 w/w; r = 1), and HMG1 at a 6-fold higher ratio, cause looping of relaxed circular DNA at 150 mM ionic strength. Oligomeric protein 'beads' are apparent at the bases of the loops and at cross-overs of DNA duplexes. (iv) HMG3 at high input ratios (r = 6), but not HMG1, causes DNA compaction without distortion of the B-form. The two HMG-box domains of HMG1 are thus capable of manipulating DNA by looping, compaction and changes in topology. The acidic C-tail down-regulates these effects by modulation of the DNA-binding properties.
TL;DR: Veratryl alcohol seemed to be playing a role in AC oxidation catalyzed by LIP in Ph. chrysosporium, and AC degradation started earlier than the production of LIP, suggesting that white rot fungi produce enzyme(s) other than LIP capable of oxidizing compounds with high ionization potential like AC.
TL;DR: In this paper, the uncoupling protein generates heat by catalyzing electrophoretic proton transport across the inner membrane of brown adipose tissue mitochondria and other monovalent anions, and both proton and anion transport are inhibited by purine nucleotides.
20 Oct 1994-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the spatial arrangement of dislocations in the grains was determined using the technique of oriented foils, characteristic of amplitudes corresponding to three regimes of cyclic stress-strain curves, and their proportions as a function of the plastic strain amplitude and the number of cycles, were evaluated.
Abstract: Dislocation structures in two heats of 316L austenitic stainless steels, cyclically strained at room temperature with constant plastic strain amplitude over a wide interval, were studied. The spatial arrangement of dislocations in the grains was determined using the technique of oriented foils. The main types of dislocation structures, characteristic of amplitudes corresponding to three regimes of cyclic stress-strain curves, and their proportions as a function of the plastic strain amplitude and the number of cycles, were evaluated. In each regime of cyclic stress-strain curve a dominant dislocation structure was found: planar dislocation arrays arranged in sheets in regime I ( ϵ ap −4 ), imperfect vein structure with persistent slip bands in the plateau regime II (1 × 10 −4 ϵ ap −3 ), and cells and wall structures in regime III ( ϵ ap > 1 × 10 −3 ).
TL;DR: In this paper, the first motion pictures of a fireball from which a meteorite has been recovered are presented, from which the ground path and the original orbit of the object are determined.
Abstract: ON 9 October 1992, a bright fireball appeared over West Virginia, travelled some 700 km in a northeasterly direction, and culminated in at least one impact: a 12.4-kg ordinary chondrite was recovered in Peekskill, New York1. Fortuitously, the event was captured on several video recordings, which provide a detailed record of both the fragmentation of the object and related atmospheric effects. These are the first motion pictures of a fireball from which a meteorite has been recovered. We report here the preliminary analysis of 14 video recordings of the event, from which we determine the ground path and the original orbit of the object.
TL;DR: The occurrence of ICDs at higher auditory centers revealed in this study, indicates peculiar processing of high frequency stimuli in normal guinea pigs.
TL;DR: In this article, the authors discuss guidelines for formation of hypotheses derived from comparing the physiological function of aspartic proteinases and sequences of their pro-parts, which are deemed important for correct folding, targeting, and control of the activation of proteinase zymogens.
TL;DR: Heat shock, cold shock and indirect chilling injury did not interfere with the continuation of pharate adult development in the flesh fly, Sarcophaga crassipalpis, but such flies failed to eclose properly when the exposure was of sufficient duration, suggesting that neuronal damage is the likely cause of injury inflicted by cold shock.
TL;DR: The nearly constant r m in terms of day‐degrees, over a wide range of temperatures, greatly simplifies the prediction of future population numbers of A. gossypii.
Abstract: Thermal requirements for development and life table statistics of Aphis gossypii Glover (Homoptera, Aphididae) were determined over a range of constant temperatures from 10 to 30 °C. The lower development threshold and the sum of effective temperatures were 6.9 °C and 90.1 °C, respectively, for preimaginal development, and 5.8 °C and 113.6 °C from birth to the onset of reproduction. Mean total fecundity ranged from 36 larvae per female at 10 °C to 76 larvae at 30 °C. On a time scale of days, net reproductive rate (Ro) increased with increasing temperature while generation time (T) decreased causing the intrinsic rate of increase (rm) to increase linearly from 0.115 to 0.465. On a day-degree scale rm only varied from 0.019 to 0.028 because the growth of Ro was compensated by an increase in T with increase in temperature. The nearly constant rm in terms of day-degrees, over a wide range of temperatures, greatly simplifies the prediction of future population numbers of A. gossypii.
TL;DR: Substituted aminomethylphenols are proposed as low-molecular mass p I markers for the electrophoretic and chromatographic focusing of ampholytes as mentioned in this paper.
TL;DR: In this paper, an efficient algorithm of the network shortest path calculation of rays and traveltimes of the first arrivals is described, and the traveltime error of such computations is estimated.
Abstract: SUMMARY An efficient algorithm of the network shortest path calculation of rays and traveltimes of the first arrivals is described. The traveltime error of such computations is estimated. The rough estimate of the relative traveltime error is evaluated locally at all network nodes prior to network ray tracing, and is minimized by means of a proper choice of the sizes of forward stars. In this way, the structure of the network is adjusted for a particular model and for a particular computer memory. After network ray tracing, the error estimate is refined and the absolute error bounds of the calculated traveltimes are evaluated. The method and its accuracy are demonstrated on numerical examples.
TL;DR: The present study demonstrates that the duration of the AC-ER amplitude increase is related to the intensity of the noise exposure (white noise, for 30 min or 1 h, intensity range 105-125 dB).
TL;DR: An overview of the theory of electrophoretic separations with special emphasis on enantiomer – chiral selector equilibria is brought, followed by a survey of indirect separations, based on formation of diastereomers with different electrophoreic mobilities.
Abstract: Capillary electrophoresis is a powerful tool for chiral separation of ionogenic enantiomers in solutions. This article brings an overview of the theory of electrophoretic separations with special emphasis on enantiomer – chiral selector equilibria, followed by a survey of indirect separations, based on formation of diastereomers with different electrophoretic mobilities, and a comprehensive appraisal of direct separations when the chiral recognition stems from (i) hostguest interactions using cyclodextrins and crown ethers as hosting agents, (ii) ligand exchange mechanism, (iii) affinity interactions or (iv) a combination of solute – chiral selector interactions with micellar electrophoretic transport. Finally, some trends in chiral separations by capillary electrophoresis are discussed.
TL;DR: In this article, the potential of a partially free mercury surface in a currentless process and at an occupied electrode under the passage of current was made less positive, and two electrons were transferred directly to the cystine SS bond in an overall irreversible process.
Journal Article•
TL;DR: It is proposed that alcuronium blocks entry to the pocket containing the [3H]NMS binding site, presumably by inducing a conformational change of the orthosteric muscarinic binding site.
Abstract: Kinetics of the interactions between the neuromuscular blocker alcuronium, the specific muscarinic antagonist N-[methyl-3H] methyl scopolamine ([3H]NMS), and muscarinic receptors were investigated in homogenates of rat heart atria. Two effects of alcuronium on the binding of [3H]NMS could be distinguished. (a) Alcuronium concentration-dependently slowed the association of [3H]NMS with receptors and the dissociation of [3H]NMS from receptors so that, at high alcuronium concentrations, equilibrium binding could not be reached, even after 20 hr, without special precautions. (b) Alcuronium increased the affinity of receptors for [3H]NMS, which was manifested by a decrease of the apparent Kd (> 3-fold) with no change in the Bmax for [3H]NMS binding. The effects of alcuronium on the rates of [3H]NMS association and dissociation can be explained only by a reaction mechanism in which [3H]NMS binds only to free receptors (not occupied by alcuronium), whereas alcuronium binds both to free receptors and to receptors occupied by [3H]NMS. Similarly, [3H]NMS cannot dissociate from receptors as long as alcuronium is attached to them. Experimental data agree with corresponding mathematical models. It is proposed that alcuronium blocks entry to the pocket containing the [3H]NMS binding site. In addition to this blocking effect, alcuronium has a positive allosteric effect on [3H]NMS binding, presumably by inducing a conformational change of the orthosteric muscarinic binding site. Earlier observations suggesting that, at high concentrations, alcuronium also competes for [3H]NMS binding sites can be explained by insufficient equilibration of the system.