showing 36 of ~574560 from 574555 documents
Non-hydrolysable macromolecular constituents from outer walls of Chlorella fusca and Nanochlorum eucaryotum
1992
Abstract Many green microalgae possess a thin trilaminar outer wall (TLS) with a very high resistance to chemical degradation. TLS are known to play an important protective role in living cells. They are also selectively preserved during fossilization and thus provide a major contribution to the fossil organic matter of a number of sedimentary rocks. However, little information is available on TLS chemical structure. Examination of the TLS of Chlorella fusca (a lacustrine Chlorophycea) and of Nanochlorum eucaryotum (a recently discovered marine Chlorophycea) indicated that (i) they exhibit morphological features commonly observed in other green microalgae, (ii) their non-hydrolysable macrom…
Histamine inhibits 5-hydroxytryptamine release from the porcine small intestine: Involvement of H3 receptors
1992
Abstract Strips of the porcine small intestine were incubated in vitro, and the release of 5-hydroxytryptamine (5-HT) was determined by high-pressure liquid chromatography with electrochemical detection. Removal of the mucosa resulted in a large reduction (95%) of tissue 5-HT, suggesting that enterochromaffin cells are the main source of 5-HT. The release of 5-HT was reduced by 70% after omission of calcium. Tetrodotoxin and hexamethonium reduced the release of 5-HT by 30%–40% in a nonadditive manner, indicating a spontaneous neuronal (nicotinic) excitatory input to the enterochromaffin cells. Histamine inhibited the release of 5-HT by about 50%. This effect was not affected by mepyramine o…
Low-temperature specific heat of orientational glasses
1992
This review summarizes specific heat data measured at low temperatures (T<1 K) on orientational glasses. Three species of mixed molecular crystals exhibiting orientational disorder are considered, namely (KBr)1−x (KCN) x , (NaCN)1−x (KCN) x (Rb)1−x (NH4) x H2PO4. For intermediate concentrations of the anisotropic components, glass-like excitations have been observed. It is demonstrated that with respect to thermal properties, orientational disorder leads to the same “universal” behaviours than for structural disorder, i.e. a specific heat which varies below 1 K and for times 10−4 s–10 s as:C p(T,t)∞T 1×ln(t). The variation of the glass-like anomaly with compositional disorder is also discus…
Das Mädchen als künftige Hausfrau und Mutter— Biologieunterricht für Mädchen im Dritten Reich
1992
Die nationalsozialistische Frauenpolitik sah im Madchen entsprechend Hitlers Forderungen nur die kunftige Hausfrau und Mutter. Gerade der Biologieunterricht, der durch die nationalsozialistische Schulreform zum Weltanschauungsunterricht aufgewertet worden war, sollte das Madchen in diesem Sinne auf seine Lebensaufgabe im Dienste der Volksgemeinschaft vorbereiten, namlich mit einem im Sinne der nationalsozialistischen Rassenlehre ausgewahlten arischen Partner moglichst viele reinrassige nordische Kinder groszuziehen.
Disassembling Papaver: a restriction site analysis of chloroplast DNA
1992
The results from a chloroplast DNA restriction site analysis of the genera Papaver and Roemeria of subf. Papaveroideae (Papaveraceae) and five outgroup taxa are presented. Papaver is represented by 14 species of eight of the 11 sections recognized, Roemeria by two of its three species. Hunnemannia fumariifolia (subf. Eschscholzioideae), Chelidonium majus (subf. Chelidonioideae), Romneya coulteri, Argemone munita and Stylomecon heterophyllum (all subf. Papaveroideae) were chosen as outgroups. DNAs were digested with 24 restriction enzymes. The major results from this analysis are: 1. Papaver, Roemeria and Stylomecon form a monophyletic group supported by at least 17 restriction site mutation…
Left ventricular diastolic and systolic function in normotensive obese subjects: influence of degree and duration of obesity.
1992
The present study was carried out to evaluate systolic and diastolic parameters in overweight and moderately obese, but otherwise healthy subjects, and in a lean control group, to determine whether degree and duration of obesity can influence left ventricular function. A total of 27 subjects, 17 overweight or with moderate obesity and 10 lean, healthy subjects were included. Patients were divided into three groups according to their body mass index (BMI) and to Garrow's criteria as follows: lean control group (BMI less than 25 kg.m-2); overweight subjects (BMI from 25 to 30 kg.m-2); moderately obese subjects (BMI greater than 30 less than 40 kg.m-2). Systolic and diastolic parameters were m…
Biomechanics of sprint running. A review.
1992
Understanding of biomechanical factors in sprint running is useful because of their critical value to performance. Some variables measured in distance running are also important in sprint running. Significant factors include: reaction time, technique, electromyographic (EMG) activity, force production, neural factors and muscle structure. Although various methodologies have been used, results are clear and conclusions can be made. The reaction time of good athletes is short, but it does not correlate with performance levels. Sprint technique has been well analysed during acceleration, constant velocity and deceleration of the velocity curve. At the beginning of the sprint run, it is importa…
Exotic hyperons: Theoretical status and search perspectives in hyperon beam facilities
1992
The theoretical models that predict the existence of exotic hyperons made of more than three quarks are reviewed. We present the properties of exotic hyperons with strangenessS=−1 (quark contents $$sqqq\bar q$$ ),S=−2 ( $$ssqq\bar q$$ ) andS=−3 ( $$sssq\bar q$$ ) predicted by the sum rules for reggeon-particle scattering amplitudes. The inclusive cross sections for the production of these hyperons in hyperon-proton interactions are calculated. The cross sections turn out to be of the order of millibarns, thus opening a good perspective to encounter such exotic hyperons in the available hyperon beam facilities at CERN and FNAL. We also propose to study the Regge trajectories corresponding to…
Transverse momentum distributions for exclusive $\varrho^{0}$ muoproduction
1992
We have studied transverse momentum distributions for exclusive rho(0) muoproduction on protons and heavier nuclei at 2 < Q2 < 25 GeV2. The Q2 dependence of the slopes of the p(t)2 and t' distributions is discussed. The influence of the non-exclusive background is investigated. The p(t)2-slope for exclusive events is 4.3 +/- 0.6 +/- 0.7 GeV-2 at large Q2. The p(t)2 spectra are much softer than inclusive p(t)2 spectra of leading hadrons produced in deep inelastic scattering.
Topical 5'-methylthioadenosine in the treatment of symptomatic chronic venous insufficiency, haemorrhoids and superficial phlebitis. A double-blind p…
1992
500 patients entered a randomised double-blind placebo-controlled trial designed to evaluate the efficacy and tolerability of topical 5′-methylthioadenosine (MTA) 0.5% in relieving the major signs and symptoms related to chronic venous insufficiency, superficial phlebitis and first and second degree haemorrhoids.
Basalt magmatism along the passive continental margin of SE Brazil (Campos basin)
1992
The SE-Brazil passive continental margin is characterized by tholeiitic magmatism that is particularly widespread in the marginal Campos basin, facing the inland flood basalts of the adjacent Parana basin. Campos magmatism is represented by Early Cretaceous (EC; 134–122 Ma) flood basalts and minor Upper Cretaceous-Early Tertiary basalt flows and intrusives, which were emplaced in a basin with attenuated crustal thickness (20 km). Petrography, mineral chemistry, wholerock geochemistry and Sr−Nd isotope composition emphasize that the EC-Campos basalts have suffered extensive seawater interaction which caused enrichment in MgO, FeO total, K2O, Rb and Ba, and depletion in SiO2 and CaO, while Zr…
Multinuclear magnetic resonance and x-ray diffraction studies of aminonitropyridines
1992
The 15N NMR spectra for 21 aminonitropyridines were measured and their chemical shifts assigned. The 1H and 13C NMR chemical shifts and spin–spin coupling constants were also determined for 16 compounds of this series. In order to relate the structural properties of nitramino groups and their 15N NMR chemical shifts in 2- and 4-nitramino-3-nitropyridines, which differ remarkably from all other amino groups studied, low-temperature 1H NMR, 17O NMR, comparative INEPT and IR spectroscopic studies were carried out. In addition, the x-ray crystal structure of 2-nitramino-3-nitropyridine was determined. Comparative spectroscopic studies showed that the nitramino derivatives exhibit different char…
LARGE-SCALE SIMULATIONS IN CONDENSED MATTER PHYSICS —THE NEED FOR A TERAFLOP COMPUTER
1992
The introduction of vector processors {“supercomputers” with a performance in the range of 109 floating point operations (1 GFLOP) per second} has had an enormous impact on computational condensed matter physics. The possibility of a substantially enhanced performance by massively parallel processors (“teraflop” machines with 1012 floating point operations per second) will allow satisfactory treatment of a large range of important scientific problems which have to a great extent thus far escaped numerical resolution. The present paper describes only a few examples (out of a long list of interesting research problems!) for which the availability of “teraflops” will allow spectacular progres…
Evidence for a two-phonon octupole vibrational state in208Pb
1992
Collective properties of206,208Pb have been investigated with gamma-ray spectroscopy using nuclear and electromagnetic excitation by208Pb projectiles. From the measurement of particle-particle-γ and particle-particle-γ γ coincidences a new energy level in208Pb at 5.683 MeV was observed and the data suggest an interpretation as a 2-phonon octupole vibrational state with spin 4+ or 6+. For this state one finds the same dynamical deformation parameterβ3 as for the first-excited collective 3− state. The results are compared to predictions of models which consider, in particular, the aspects of the quadrupole interaction and the interaction of the 2-particle pairing vibration with the 2-phonon o…
Changes in biochemical composition of gills, hepatopancreas and muscle of the red crayfish Procambarus clarkii (Girard) after sublethal exposure to m…
1992
Abstract 1. 1. The changes in the biochemical composition of gills, hepatopancreas and muscle after exposure to 0.25 mg Hg/l were studied in Procambarus clarkii . 2. 2. Sublethal exposure to mercury in P. clarkii resulted in significant decreases in protein concentration and caloric concentration in gills over the 96 hr period. Glycogen/lipid and glycogen/protein ratios increased after 48 and 96 hr of mercury exposure. 3. 3. Lipid and caloric concentration in the hepatopancreas were significantly lower in 96 hr mercury exposed group. 4. 4. Glycogen concentration in muscle was depleted as consequence of 96 hr mercury exposure.
A measurement of the decay KL→π0γγ
1992
Abstract The full data set of the experiment NA31 at CERN has been used to analyse the decay mode KL→π0γγ. A signal of 63 events has been observed with an estimated background of 6.0±1.7 events, corresponding to a branching ratio of (1.7±0.3)×10−6 consistent with our previous result based on partial statistics. The invariant mass spectrum of the two photons is found to be consistent with chiral perturbation theory, and the decay is dominated by the J = 0 two photon state.
A muscarinic receptor different from the M1, M2, M3 and M4 subtypes mediates the contraction of the rabbit iris sphincter
1992
In order to analyse the subtype of muscarinic receptors involved in the methacholine-induced contraction of the rabbit iris sphincter we have determined equilibrium dissociation constants (KB) of various antagonists in the sphincter muscle. The values were compared with those observed at M1 (rabbit vas deferens), M2 (heteroreceptors in rat iris) and M3 receptors (guinea-pig ileum), or at the muscarinic receptors in the guinea-pig uterus. The methacholine-induced contraction of the uterus from immature guinea-pigs was competitively antagonized by pirenzepine (6.64, -log KB), 4-DAMP (8.39), hexahydrodifenidol (HHD; 7.00 for the (R)- and 5.40 for the (S)-enantiomer), p-fluoro-hexahydrosiladife…
Localization of Ca(2+)-stores and tissue compartments with a Ca(2+)-binding capacity in the organ of Corti of the guinea-pig by electron energy-loss …
1992
SUMMARY The addition of 10 mM CaCl2 to glutaraldehyde fixative leads to the formation of small electron-dense deposits in the organ of Corti of the guinea-pig. These precipitates are mainly attached to cell membranes in contact with different extracellular lymphatic fluids. A higher number of precipitates is localized in the acellular parts of tectorial and basilar membrane. Electron energy-loss spectroscopy (EELS) was used to determine the elemental composition of the deposits formed. The spectra showed a prominent signal at the Ca2+ L2,3 ionization edge. Oxygen could also be detected in all the precipitates analysed. EELS analysis of mitochondria of the inner and outer hair cells after co…
A novel galactose- and arabinose-specific lectin from the sponge Pellina semitubulosa: isolation, characterization and immunobiological properties.
1992
A new lectin from the sponge Pellina semitubulosa is derived which was extracted and purified to homogeneity. The purified lectin is probably a hexamer of polypeptide chains (each M(r) 34,000) which are covalently linked via disulfide linkages; the isoelectric point is 6.1. The lectin displays the following specificities: D-galactose (50% inhibition of hemagglutination at 0.2 mM) = L-arabinose (0.2 mM) greater than D-fucose (1.5 mM) greater than D-glucose (3.0 mM). It precipitates human erythrocytes (A1, A2, A1B, B, and O) with a titer between 2(8) and 2(11) and erythrocytes from sheep and rabbits with a titer between 2(5) and 2(10). The Pellina lectin displays a strong mitogenic effect on …
Two tissue-specific loci for octopine dehydrogenase in Tapes Decussatus (Bivalvia, Veneridae)
1992
Abstract 1. 1. Octopine dehydrogenase catalyses the reductive condensation of pyruvate and arginine to produce octopine in mollusc tissues. 2. 2. In all Bivalvia species studied to date, a single polymorphic locus, anodally migrating, was demonstrated. 3. 3. We studied, by starch gel electrophoresis, octopine isozymes in Tapes decussatus tissues. 4. 4. A polymorphic anodal form is present in adductor muscle, foot muscle, mantle and gill. 5. 5. A hepatopancreas-specific form, cathodally migrating, is also evident.
Study of the phase composition of iron-containing Langmuir-Blodgett layers before and after thermal and chemical treatment
1992
Iron-containing Langmuir–Blodgett mono- and multilayers were prepared by depositing ferric stearate onto silicon wafers. Particular care should be taken in order to avoid the presence of alkali ions, which may replace iron ions in the deposited film. By a subsequent heating in air, the fatty acid chains were thermodesorbed. This results in a rather homogeneous coating of the samples by an iron oxide, most probably in the form of crystalline and amorphous γ-FeOOH, as found by conversion electron Mossbauer, photoelectron and microprobe studies. By a subsequent heating in hydrogen gas or exposure to nascent hydrogen, a partial reduction of the iron oxide layer is possible up to the metallic st…
Generalized on-shell renormalization of heavy quarks
1992
A generalized on-shell (GOS) renormalization scheme of QCD is developed to evaluate the renormalization of heavy quark wave functions and currents. All large logarithms arising from the physical range of quark masses and momentum transferq 2 can be absorbed into wave function and vertex renormalization. Our results are more general than those of the heavy quark effective theory and agree with the latter only at zero recoil. The proposed GOS scheme is very suitable for the μ/m Q expansion. As an application we discuss the renormalization of the flavour changing currentsb-c, t-b andt-c.
LiquidHe4andHe3at negative pressure
1992
The critical pressures {ital P}{sub {ital c}} at which liquid {sup 4}He and {sup 3}He each become macroscopically unstable are determined from two kinds of microscopic calculations that reproduce the equation of state. The behavior of the sound velocity {ital c} around this critical pressure is analyzed, and the critical exponent in {ital c}{proportional to}({ital P}{minus}{ital P}{sub {ital c}}){sup {nu}} is found to be {nu}=1/4. A comparison with empirical analysis is also done.
Faszikuläre und subfaszikuläre Architektur der Ligamenta cruciata
1992
Morphologie der Kollagenfaszikel und Vaskularisationsdichte von vorderem und hinterem Kreuzband wurden durch kombinierte histologische, transmissions- und rasterelektronenmikroskopische, morphometrische und immunhistochemische Studien analysiert. Die Fibrillendurchmesser im vorderen Kreuzband lagen zwischen 20 und 155 nm (x=74 nm, s=18.8 nm) und im hinteren Kreuzband zwischen 20 und 175 nm (x=82 nm, s=25,4 nm). Kollagen Typ III und VI besasen ein diffuses Verteilungsmuster mit einem Maximum in der Ansatzzone der Bander. Der Kollagen-Typ-IV-Gehalt des vorderen Kreuzbandes war gering. Die Anzahl der Kreuzbandarteriolen zeigte ein charakteristisches Verteilungsmuster (vorderes Kreuzband: unter…
An acid extract from dissociation medium of sea urchin embryos, induces mesenchyme differentiation
1992
Abstract When material extracted by 1 M acetic acid from the dissociation medium of sea urchin embryos is added at low concentrations to isolated primary mesenchyme cells, it induces skeletogenesis. The same material added to dissociated blastula cells, or to embryos at the blastula stage, stimulates skeleton formation and pigment cell differentiation. On dissociated cells, it also increases cell reaggregation, thymidine incorporation and survival. On embryos, it induces exogastrulation and appearence of extraembryonic pigment cells. The activity of the extract is resistant to raised temperatures and partially to tryptic digestion but is abolished by trypsin treatment followed by heating. T…
Post‐Soviet Reform in Latvia: Early Progress and Future Prospects
1992
After the rapid and dramatic demise of the Soviet Union in 1991, 15 newly autonomous republics are restructuring their economies after decades of central Communist planning. The three Baltic states of Latvia, Lithuania and Estonia had successful market‐oriented economies during more than two decades of independence between World Wars I and II and were comparatively strong performers within the USSR after being occupied in 1940. A case study of Latvia looks at the historic factors and political issues which are shaping the current reform process. A contrast of state‐run, collective and private enterprises is used to illustrate the rapid changes which now place Latvia at the forefront among p…
The effects of the macrocyclic lactone bryostatin-1 on leukemic cells in vitro.
1992
The macrocyclic lactone bryostatin-1 was found to exert in vitro antineoplastic activity against several leukemic cell lines, including human K562 erythroleukemia, HL60 promyelocytic leukemia, REH and MOLT-4 lymphoblastic leukemias, CCRFCEM lymphoma, KG-1 myeloid leukemia, and murine P388 lymphocytic leukemia. No statistically significant difference in sensitivity to bryostatin-1 was found between adriamycin-resistant P388 and K526 subclones and their sensitive counterparts. Freshly explanted clonogenic leukemic cells showed a variable sensitivity to bryostatin-1 in 10/12 tested samples. The IC50 of clonogenic leukemic cells was 4 × 10–3 M bryostatin-1, and that of normal marrow CFU-GM was…
Optimized analysis of the critical behavior in polymer mixtures from Monte Carlo simulations
1992
A complete outline is given for how to determine the critical properties of polymer mixtures with extrapolation methods similar to the Ferrenberg-Swendsen techniques recently devised for spin systems. By measuring not only averages but the whole distribution of the quantities of interest, it is possible to extrapolate the data obtained in only a few simulations nearT c over the entire critical region, thereby saving at least 90% of the computer time normally needed to locate susceptibility peaks or cumulant intersections and still getting more precise results. A complete picture of the critical properties of polymer mixtures in the thermodynamic limit is then obtained with finite-size scali…
Changes of the Quantum Yield of Oxygen Evolution and the Electron Transport Capacity of Isolated Spinach Thylakoids during Photoinhibition
1992
Summary Isolated spinach thylakoids can be protected from photoinhibitory loss of electron transport capacity by the radical defense system composed of the enzymes SOD and catalase, as well as the antioxidants glutathione and ascorbate. With these compounds present at saturating concentrations, thylakoids not only retain a high photochemical capacity but also do not suffer D1-protein degradation during photoinhibition. However, a strong decrease in the quantum yield of oxygen evolution, Φ O 2 , occurs with the same thylakoids. These results support the view that the photochemical capacity and the quantum yield of oxygen evolution decline due to different mechanisms during photoinhibition. T…
Incoherent quasi-elastic neutron scattering in isomeric alcohols
1992
Abstract Incoherent quasi-elastic neutron scattering (IQENS) data on liquid isomeric alcohols normal-pentanol (n-PeOH) and 2-methyl-2-butanol (2M-2BuOH) and on their mixture are presented. The diffusive motion of protons, as a function of temperature, is analyzed in the framework of the random jump diffusion model. The temperature dependence of the parameters obtained confirms the more “fragile” behaviour of the more sterically hindered 2M-2BuOH with respect to that of the linear n-PeOH.
Synthesis of vinca alkaloids and related compounds LX. A simple transformation of apovincamine into vincamine
1992
Abstract The 15α-chloro-vincamine derivative 2 was prepared and proved to be key intermediate of a two-step transformation of apovincamine into vincamine. The structure of 2 was established via detailed NMR and X-ray investigations.
MR-Tomographie bei Hodenprozessen
1992
The value of T1-weighted sequences after intravenous administration of Gd-DTPA and of T2-weighted sequences was compared in 43 patients suspected of having scrotal abnormalities. T2-weighted sequences gave better demonstration of the tunica albuginea and better contrast between tumor and parenchyma. The two techniques were equally sensitive for demonstrating testicular tumors but orchitis was better demonstrated on the contrast enhanced sequences. Motion artifacts were less marked in the T1-weighted sequences with contrast enhancement. In selected cases, contrast enhancement may be a valuable addition to native protocols. Our experience has indicated that MRI provides specific findings in c…
Synthesis ofo-thiatelluraphenylenezirconocenes. X-ray crystal structure of
1992
o-Thiatelluraphenylenezirconocene complexes were obtained in good yield by reaction of dilithiumo-benzenthiatelluride with zirconocene dichlorides. These compounds represent the first examples of heterodichalcogenaphenylene bent metallocences. They were characterized by spectroscopic methods and the effect on the n.m.r. results of stepwise substitution of one and two Te atoms for S is discussed.
Effects of cyclic fatty acid monomers on the function of cultured rat cardiac myocytes in normoxia and hypoxia
1992
Abstract It was shown in a previous study that rat ventricular myocytes in culture do incorporate in their phospholipids the cyclic fatty acid monomers (CFAM), produced from linolenic acid by heating linseed oil. In the present study, the functional consequences of this incorporation were investigated. As compared to control cells, CFAM containing cells displayed altered electromechanical properties evidenced by decreased maximal diastolic potential, upstroke velocity and rate and a shortened action potential duration. Moreover, oxygen depletion exerted much more adverse effects on CFAM-treated cells than in control cells, such as spontaneous rhythm abnormalities, cell shortening failure an…
Effects of Calcium Antagonists on Rat Normal and Skinned Fundus
1992
Abstract Calcium chloride (CaCl2) (0·1−25 Mm, in K+-depolarized tissue), KCl (10−112 Mm) and acetylcholine (1 × 10−9 m−1 Mm) produced concentration-dependent contractions of rat isolated fundus. Verapamil (0·01−100 μm), cinnarizine (1−100 μm), trifluoperazine (10−500 μm) and dantrolene (50−250 μm) each produced a concentration-related rightward and downward shift of the log concentration-effect curve for CaCl2. The rank order of potencies of these antagonists, measured as the IC50 against Ca2+ (25 Mm)-induced contraction of depolarized fundus, was verapamil (2.5 μm) &gt; cinnarizine (8·7 μm) &gt; trifluoperazine (85·1 μm) &gt; dantrolene (&gt; 250 μm). Cinnarizine (0·5 Mm) a…
Synthesis, configuration, and calcium modulatory properties of enantiomerically pure 5-oxo-1,4,5,6,7,8-hexahydroquinoline-3-carboxylates.
1992
Enantiomerically pure hexahydroquinolinones of the structural type 9 were prepared by a variation of the Hantzsch synthesis in which an optically active acetoacetate served as a chiral auxiliary reagent. Determinations of the de and ee values are described. The absolute configurations of the optically pure products were characterized by single-crystal X-ray analysis. The antipodes 9a and 9b exhibited calcium antagonistic activities on smooth musculature; the (S)-(-)-enantiomer 9b was the more potent compound with regard to the EC50 values which differed by a factor of 100; the intrinsic activity of 9b was 1.2, compared with a value of 0.54 for 9a. On the other hand, R-(+)-9a exerted positiv…