Showing papers by "University of Würzburg published in 1984"
TL;DR: Constant internal CO2 may aid in minimizing photoinhibition during stomatal closure at midday, and the effects on capacity, slope, and compensation point were reversed by lowering the temperature and increasing the humidity in the afternoon.
Abstract: The carbon-dioxide response of photosynthesis of leaves of Quercus suber, a sclerophyllous species of the European Mediterranean region, was studied as a function of time of day at the end of the summer dry season in the natural habitat. To examine the response experimentally, a "standard" time course for temperature and humidity, which resembled natural conditions, was imposed on the leaves, and the CO2 pressure external to the leaves on subsequent days was varied. The particular temperature and humidity conditions chosen were those which elicited a strong stomatal closure at midday and the simultaneous depression of net CO2 uptake. Midday depression of CO2 uptake is the result of i) a decrease in CO2-saturated photosynthetic capacity after light saturation is reached in the early morning, ii) a decrease in the initial slope of the CO2 response curve (carboxylation efficiency), and iii) a substantial increase in the CO2 compensation point caused by an increase in leaf temperature and a decrease in humidity. As a consequence of the changes in photosynthesis, the internal leaf CO2 pressure remained essentially constant despite stomatal closure. The effects on capacity, slope, and compensation point were reversed by lowering the temperature and increasing the humidity in the afternoon. Constant internal CO2 may aid in minimizing photoinhibition during stomatal closure at midday. The results are discussed in terms of possible temperature, humidity, and hormonal effects on photosynthesis.
210 citations
TL;DR: Calculations revealed that the enzymatic apparatus responsible for the reduction of 3-phosphoglycerate to dihydroxyacetone phosphate is not displaced much from equilibrium even under maximum rates of photosynthesis at saturating CO2, and fructose-1,6-bisphosphate did not limit Calvin cycle turnover.
205 citations
TL;DR: Investigation of the Kiel classification of non‐Hodgkin lymphomas found marked improvement of prognosis was solely possible by induction of complete remissions whereas in corresponding low‐grade malignant lymphomas also partial remissions were prognostically relevant.
Abstract: Clinical and prognostic relevance of the Kiel classification of non-Hodgkin lymphomas (NHL) was investigated in 1127 patients entering a prospective multicenter observation study Survival of the 782 (694 per cent) patients with low-grade malignant NHL (lymphocytic lymphomas, predominantly B-CLL, LP immunocytoma, centrocytic lymphoma, centroblastic-centrocytic lymphoma) exceeded that of the 341 patients (302 per cent) with high-grade malignant NHL (centroblastic, immunoblastic, lymphoblastic lymphomas) Prognosis was best in centroblastic-centrocytic lymphoma and in B-CLL and least favorable in immunoblastic and lymphoblastic lymphomas Survival of LP immunocytoma and centrocytic lymphoma patients was intermediate after 2 to 25 years of follow-up Corresponding to histopathology, pattern of survival curves of low-grade malignant NHL (slow decline, no plateauing) differed from that of high-grade malignant NHL (rapid decline, subsequent plateauing) Prognosis of B-CLL was superior to that of LP immunocytoma Stages I and II were more frequent in centroblastic-centrocytic lymphoma (21 per cent) than in LP immunocytoma (25 per cent) and centrocytic lymphoma (11 per cent) Ability of radiotherapy to induce stable complete remissions in stage III of centroblastic-centrocytic lymphoma indicates prolonged restriction of lymphoma to the lymphatic system In immunoblastic and centroblastic lymphomas, stages I and II were diagnosed in 34 and 38 per cent of cases, respectively, but only in stage I/IE of centroblastic lymphoma prolonged remissions were achieved by radiotherapy In advanced high-grade malignant NHL marked improvement of prognosis was solely possible by induction of complete remissions whereas in corresponding low-grade malignant lymphomas also partial remissions were prognostically relevant
204 citations
TL;DR: This is the first case that, in a higher eukaryote, the complete structure is known of both the natural suppressor tRNAs and the corresponding viral RNA on which they exert their function.
Abstract: The hypothetical replicase or replicase subunit cistron in the 5'-proximal part of tobacco mosaic virus (TMV) RNA yields a major 126-K protein and a minor 183-K ;readthrough' protein in vivo and in vitro. Two natural suppressor tRNAs were purified from uninfected tobacco plants on the basis of their ability to promote readthrough over the corresponding UAG termination codon in vitro. In a reticulocyte lysate the yield of 183-K readthrough protein increases from 10% in the absence of added tobacco plant tRNA up to 35% in the case of pure tRNA added. Their amino acid acceptance and anticodon sequence (GpsiA) identifies the two natural suppressor tRNAs as the two normal major cytoplasmic tyrosine-specific tRNAs. tRNA(1) has an A:U pair at the base of the TpsiC stem and an unmodified G(10), whereas tRNA(2) contains a G:C pair in the corresponding location and mG in position 10. This is the first case that, in a higher eukaryote, the complete structure is known of both the natural suppressor tRNAs and the corresponding viral RNA on which they exert their function. The corresponding codon-anticodon interaction, which is not in accordance with the wobble hypothesis, and the possible biological significance of the readthrough phenomenon is discussed.
163 citations
TL;DR: It is reported that T4+ TLC can acquire specific cytotoxicity during in vitro cultivation.
Abstract: Mature human T lymphocytes can be separated by monoclonal antibodies OKT4 and OKT8 according to their surface phenotypes into T4+T8− and T4−T8+ subsets1,2. From shortterm experiments using bulk cultures, the helper/inducer function has been assigned to the T4+T8− subset and the cytotoxic/suppressor function to the T4−T8+ subset1,2. Thus if T lymphocytes are separated after stimulation in a mixed lymphocyte reaction (MLR), the entire cytotoxic activity is found hi the T4−T8+ fraction whereas the T4+T8− fraction shows no detectable cytotoxicity1. If, however, T lymphocytes are cloned after MLR and grown in long-term culture, a surprisingly large fraction of T4+ T lymphocyte clones (TLC) shows cytotoxic activity3,4. Here we report that T4+ TLC can acquire specific cytotoxicity during in vitro cultivation.
152 citations
TL;DR: Bio-monitoring of hemoglobin-bound metabolites represents a novel approach to control exposure to potential carcinogens, to correlate environmental exposure with tissue dose and eventually also with human risk.
Abstract: Genotoxic xenobiotics bind covalently to hemoglobin in vivo. The major reaction product of aromatic amines is a sulfinic acid amide resulting from the reaction of arylnitroso derivatives with SH-groups. Alkylating compounds react with cysteine, histidine and the terminal valine. The adducts are formed proportional to dose down to extremely small doses, they are stable throughout the life-span of the erythrocytes and accumulate upon repeated exposure. Methods for their determination in blood samples from experimental animals and humans are becoming available. Moreover, it has been demonstrated that for a given agent, a constant ratio exists between the reaction with tissue DNA and hemoglobin over a wide range of doses, which indicates that the reactions follow apparent first order kinetics. The extent of hemoglobin binding is therefore considered to be a relative measure of tissue dose, and should correlate much better with risk than exposure levels calculated from concentrations in the environment. Not only can the actual uptake be monitored more reliably, but also the individual's capacity to metabolically activate the absorbed agent. Biomonitoring of hemoglobin-bound metabolites represents a novel approach to control exposure to potential carcinogens, to correlate environmental exposure with tissue dose and eventually also with human risk.
151 citations
TL;DR: The fluorescence assay provides a rapid and reliable means of determining the heat tolerance limit of leaf tissue and shows that heat-induced fluorescence changes within the thylakoid membrane may be connected with the irreversible leaf tissue damage which occurs following prolonged exposure to high temperature.
Abstract: Heat tolerance limits for a variety of vascular plant leaves were determined both with the conventional post-culture necrosis method and by measurements of the heat-induced increase in chlorophyll fluorescence (F-T curves). The reliability of the fluorescence test was improved with the addition of far-red background light which counteracts dark reduction of the Photosystem II acceptor pool by heat-stimulated endogenous electron donors. This was of particular importance in the case of xeromorphic leaves in which the diffusion barrier for oxygen is high. A satisfactory correlation was found between T
L50, the temperature at which a 30 min exposure results in 50% necrotic leaf area following post culture, and the critical temperature, T
c
,the temperature at which the dark fluorescence level begins to increase during slow heating of a leaf sample at a rate of 0.7 K min-1, in the fluorescence test. The correlation can be described by a linear function, T
L50=1.12 T
c
-5.37,with a correlation coefficient, r=0.87. Maximal deviation of the regression line from the line T
L50=T
c
was 1.2 K, with 22 determinations for leaves with widely varying heat tolerance limits. This shows that heat-induced fluorescence changes within the thylakoid membrane may be connected with the irreversible leaf tissue damage which occurs following prolonged exposure to high temperature. On the basis of the heat dosage equation of Lepeschkin, a more general expression can be obtained which allows calculation of the accumulated heat dosage under the experimental conditions of the standard fluorescence test (slow heating, 0.7 K min-1). Such calculations reveal that for a given species the ‘fraction of critical dosage’ begins to increase, i.e. accumulating heat reaches an injurious level, at a temperature which approximately coincides both with T
L50, obtained with the necrosis method, and with T
c
,the critical temperature derived from the fluorescence test. Hence, the increase in fraction of critical dosage and the rise in chlorophyll fluorescence seem to concur. It is concluded that the fluorescence assay provides a rapid and reliable means of determining the heat tolerance limit of leaf tissue.
149 citations
TL;DR: Injections of juvenile hormone and 20-hydroxyecdysone, separately and simultaneously, significantly increased the probability that the treated female would be the dominant female of a test pair.
Abstract: Laboratory studies on overwintered foundresses of Polistes gallicus show that differences in the endocrine activity are mainly responsible for achieving the dominance rank. Females that became dominant had either larger corpora allata or more developed ovaries than subordinate females. Body size did not contribute to dominance rank. Since a correlation exists between the length of terminal oocytes and the ecdysteroid titre in haemolymph as well as between the volume of corpora allata and the synthesis of juvenile hormone, dominant behaviour is thought to depend upon an elevated hormone titre in haemolymph. Injections of juvenile hormone (JHI) and 20-hydroxyecdysone, separately and simultaneously, significantly increased the probability that the treated female would be the dominant female of a test pair. After a hierarchy has been established, endocrine activity in subordinate foundresses is inhibited by the dominant foundress that then monopolizes reproduction.
137 citations
TL;DR: Les spectres de photoemission a resolution de moment de Cu(110) presentent une structure a 4 eV au-dessus de l'energie de Fermi en bande interdite en volume as mentioned in this paper.
Abstract: Les spectres de photoemission a resolution de moment de Cu(110) presentent une structure a 4 eV au-dessus de l'energie de Fermi en bande interdite en volume. Cette emission presente une dispersion de type electron libre
134 citations
TL;DR: The mitotic and meiotic chromosomes of the American cyprinodont fish Poecilia sphenops var.
Abstract: The mitotic and meiotic chromosomes of the American cyprinodont fish Poecilia sphenops var. melanistica were analysed. All 46 chromosomes are telocentric. By specific staining of the constitutive heterochromatin with C-banding and various AT-specific fluorochromes, the homomorphic chromosome pair 1 could be identified as sex chromosomes of the ZW/ZZ type. All female animals exhibit a W chromosome with a large region of telomeric heterochromatin that is not present in the Z chromosome. These sex chromosomes cannot be distinguished by conventional staining; they represent the first demonstration of sex chromosomes in fishes in an early stage of morphological differentiation. The W heterochromatin and the telomeric heterochromatin in the two autosomes 18 show a very bright fluorescence when stained with AT-specific fluorochromes. This allows the direct identification of the chromosomal sex by examining the interphase nuclei: females exhibit three, males only two brightly fluorescent heterochromatic chromocenters in their nuclei. The significance of these ZW/ ZZ sex chromosomes and their specific DNA sequences, the dose compensation of the Z-linked genes, and the experimental possibilities using sex-reversed “ZW males” are discussed.
123 citations
TL;DR: Rates of sucrose transfer across the tonoplast were even higher in vitro than in vivo indicating that the sucrose transport system had not suffered damage during isolation of the vacuoles.
Abstract: Sucrose transport has been investigated in vacuoles isolated from barley mesophyll protoplasts. Rates of sucrose transfer across the tonoplast were even higher in vitro than in vivo indicating that the sucrose transport system had not suffered damage during isolation of the vacuoles. Sucrose transport is carrier-mediated as shown by substrate saturation of transport and sensitivity to a metabolic inhibitor and to competitive substrates. A number of sugars, in particular maltose and raffinose, decreased uptake of sucrose. Sorbitol was slowly taken up but had no effect on sucrose transport. The SH-reagent p-chloromercuribenzene sulfonate inhibited sucrose uptake completely. The apparent Km of the carrier for sucrose uptake was 21 mM. Transport was neither influenced by ATP and pyrophosphate, with or without Mg2+ present, nor by protonophores and valinomycin (with K+ present). Apparently uptake was not energy dependent. Efflux experiments with preloaded vacuoles indicated that sucrose unloading from the isolated vavuoles is mediated by the same carrier which catalyses uptake. The vacuole of mesophyll cells appears to represent an intermediary storage compartment. Uptake of photosynthetic products into the vacuole during the light apparently minimizes osmotic swelling of the small cytosolic compartment of vacuolated leaf cells when photosynthetic productivity exceeds the capacity of the phloem for translocation of sugars.
TL;DR: The study provides evidence that the measurement of Ca/Cr ratios in untimed random urine specimens during the post-absorptive state may be a reasonable screening test for elevated Ca excretion and that idiopathic hypercalciuria seems to be as prevalent in children as it is in adults.
Abstract: Hypercalciuria is of continuing interest as on of the risk factors for stone disease in children, but the definition, incidence and pathogenesis are controversial. Therefore reference values for the urinary calcium/creatinine (Ca/Cr) ratios were established in 564 healthy children aged 6–17.9 years during the fasting state (09.00 h) and in 236 of them also in the post-absorptive state about 2 h after lunch (14.00–16.00 h). The Ca/Cr ratios in both urine specimens were independent of age and sex, rendering it possible to determine a common normal range and to calculate centiles for Ca excretion in a large sample of healthy children and adolescents. To provide information about the incidence of hypercalciuria the Ca/Cr ratios of 1013 other apparently healthy children aged 6–17.9 years were measured during the post-absorptive state on two consecutive days. In 39 (3.8%) of them, 21 girls, and 18 boys, the Ca excretion was elevated in both urine specimens. Thirtysix of these children, all presenting without renal complaints, underwent further investigations to elucidate the possible mechanisms of the hypercalciuria.
TL;DR: In human male subjects, HAAE was also identified as a urinary metabolite of Tri after exposure of two volunteers to 200 ppm Tri for 6 hr, indicating hydrolytic dechlorination reactions in the metabolism of Tri.
TL;DR: Optimum conditions required for inducing the various types of undercondensation in the chromosomes were determined and various examples of the use 5-azacytidine in the analysis of chromosome rearrangements involving heterochromatic regions are presented.
Abstract: The cytosine analogue 5-azacytidine induces very distinct undercondensations in human chromosomes if applied to lymphocyte cultures. The number of induced undercondensations and their chromosomal localization can be varied by the 5-azacytidine dose and the treatment time. “Pulverized” chromosomes or undercondensations in the G-band-positive chromosome regions are produced with high doses and long treatment times. If applied in low doses during the last hours of culture, 5-azacytidine induces specific undercondensations in the heterochromatin of chromosomes 1, 9, 15, 16, and Y. Optimum conditions required for inducing the various types of undercondensation in the chromosomes were determined. Various examples of the use 5-azacytidine in the analysis of chromosome rearrangements involving heterochromatic regions are presented.
TL;DR: The possibility of Ap4A being a 'second messenger' of cell cycle and proliferation control is discussed in the light of these results and those reported previously demonstrating thatAp4A is a ligand of mammalian DNA polymerase alpha, triggers DNA replication in quiescent mammalian cells and is active in priming DNA synthesis.
Abstract: An assay of adenosine(5′)tetraphospho(5′)adenosine (Ap4A), based on the luciferin/luciferase method for ATP measurement, was developed, which allows one to determine picomolar amounts of unlabeled Ap4A in cellular extracts. In eukaryotic cells this method yielded levels of Ap4A varying from 0.01 μM to 13 μM depending on the growth, cell cycle, transformation, and differentiation state of cells. After mitogenic stimulation of G1-arrested mouse 3T3 and baby hamster kidney fibroblasts the Ap4A pools gradually increased 1000-fold during progression through the G1 phase reaching maximum Ap4A concentrations of about 10 μM in the S phase. Quiescent 3T3 cells reach a high level of Ap4A (1 μM) in a “committed” but prereplicative state if exposed to an external mitogenic stimulant (excess of serum) and simultaneously to a synchronizer which inhibits entry into the S phase (hydroxyurea). When the block for DNA replication was removed at varying times after removal of the stimulant decay of commitment to DNA synthesis was found correlated with a shrinkage of the Ap4A pool. Cells lacking a defined G1 phase (V79 lung fibroblasts, Physarum) possess a constitutively high base level of Ap4A (about 0.3 μM) even during mitosis. From this high level, Ap4A concentration increases only about tenfold during the S phase. Temperature-down-shift experiments, using chick embryo cells infected with transformation-defective temperature-sensitive viral mutants(td-ts), have shown that the expression of the transformed state at 35°C is accompanied by a tenfold increase of the cellular Ap4A pool. Treatment of exponentially growing human cells with interferon leads, concomitantly with an inhibition of DNA syntheses, to a tenfold decrease in intracellular Ap4A levels within 20 h. The possibility of Ap4A being a “second messenger” of cell cycle and proliferation control is discussed in the light of these results and those reported previously demonstrating that Ap4A is a ligand of mammalian DNA polymerase α, triggers DNA replication in quiescent mammalian cells and is active in priming DNA synthesis.
TL;DR: In this paper, the lattice parameters of the hexagonal unit cell, the atomic parameters, and the shift of the Raman active vibrations are measured of p-Bi2Te3 under uniaxial and hydrostatic pressure.
Abstract: The lattice parameters of the hexagonal unit cell, the atomic parameters, and the shift of the Raman active vibrations are measured of p-Bi2Te3 under uniaxial and hydrostatic pressure. The structural investigations are performed by neutron diffraction, and the lattice vibrations are studied by Raman scattering. The results of the diffraction experiments constitute a direct experimental confirmation of the weak bonding between the sandwiches in this narrow gap semiconductor with sandwich structure. As a consequence, some Raman active phonon modes show a rather strong dependence upon uniaxial pressure up to Δṽ/Δp = 1.9 × 10−8cm−1/Pa.
Die Gitterparameter der hexagonalen Einheitszelle, die Atompositionen und die Verschiebung der Raman-aktiven Gitterschwingungen von p-Bi2Te3 unter uniaxialem und hydrostatischem Druck werden gemessen. Die strukturellen Untersuchungen werden mittels Neutronenbeugung durchgefuhrt, die Gitterschwingungen mit Ramanstreuung untersucht. Die Ergebnisse der Diffraktions-experimente konstatieren einen direkten experimentellen Beweis fur die schwachen Bindungen zwischen den Sandwiches in diesem Schmalband-Halbleiter mit Sandwichstruktur. Als Konsequenz zeigen einige Raman-aktive Gitterschwingungen eine relativ starke Druckabhangigkeit der Anregungsfrequenzen, unter uniaxialem Druck bis zu Δṽ/Δp = 1,9 × 10−8cm−1/Pa.
TL;DR: The data demonstrate the potential use of chromosome-specific repetitive DNA probes to study the problem of interphase chromosome topography and indicate a large variability of the distances between the sex chromosomes in male and female interphase nuclei.
Abstract: Summary. Two cloned repetitive DNA probes, pXBR and CY1, which bind preferentially to specific regions of the human X and Y chromosome, respectively, were used to study the distribution of the sex chromosomes in human lymphocyte nuclei by in situ hybridization experiments. Our data indicate a large variability of the distances between the sex chromosomes in male and female interphase nuclei. However, the mean distance observed between the X and Y chromosome was significantly smaller than the mean distance observed between the two X-chromosomes. The distribution of distances determined experimentally is compared with three model distributions of distances, and the question of a non-random distribution of sex chromosomes is discussed. Mathematical details of these model distributions are provided in an Appendix to this paper. In the case of a human translocation chromosome (Xqter---~ Xp22.2: :Yq11--->Yqter) contained in the Chinese hamster x human hybrid cell line 445 x 393, the binding sites of pXBR and CY1 were found close to each other in most interphase nuclei. These data demonstrate the potential use of chromosome-specific repetitive DNA probes to study the problem of interphase chromosome topography.
TL;DR: A partir des structures cristallines de 160 complexes metalliques du carbene sont etudies la liaison metal-carbone de ces complexes and l'influence du reste de la molecule sur cette liaison, en vue d'expliquer la catalyse et la stœchiometrie des reactions of ces complex.
TL;DR: A significant correlation was found between the te Jerichoic acid structure and the serogroups of Listeria, suggesting that cell wall teichoic acids are immunochemical determinants of Listersia strains.
TL;DR: In this paper, a 1,3-Dipolar cycloaddition of nitrile oxides, generated from nitroethanol and nitroacetaldehyde derivatives 3, 21 and 22, respectively, and of benzonitrile oxide to 4-vinyldioxolanes 1, 2 gave ca 4:1 erythro/threo mixtures of corresponding isoxazolines.
TL;DR: Application of this assay in cases of SSPE, mumps meningitis and herpes simplex encephalitis demonstrates sensitivity and possible suitability of this technique for use in diagnosis of virus infections of the central nervous system.
TL;DR: The results of 10 years of patch tests in children with eczema aged between 3 and 16 years are reported, with a total of 5,064 negative tests among 141 children.
Abstract: The results of 10 years of patch tests in children with eczema aged between 3 and 16 years are reported. 147 children were tested, of whom 104(71 %) reacted. 334(6.1%) of 5398 tests were positive and 302 were relevant. 3,539 tests were negative in the 104 children who reacted to at least one substance. 1,525 negative tests were found in 43 children who showed no positive reactions, making a total of 5,064 negative tests among 141 children.
The conclusions are: (i) Positive tests are relatively infrequent in children in relation to the large number of tests performed, (ii) The high number of negative results shows that the skin of children can be tested with the concentrations used for adults, and supports the allergic nature of the positive reactions in the series, which were relevant in 90% of the patients.
TL;DR: Different strains ofListeria monocytogenes serovar 1/2a were used to infect mice and there is no increased susceptibility of the avirulent bacteria to these defence mechanisms, and other bacterial properties, such as serum sensitivity and lysozyme susceptibility, are considered to be unimportant.
Abstract: Different strains ofListeria monocytogenes serovar 1/2a were used to infect mice. A smooth, haemolytic strain multiplied in the spleen of normal adult mice and induced a long-lasting immunity to subsequent challenge infection. When the animals were treated with dextran sulphate (DS)Listeriae multiplied more rapidly and death followed within a few days. When normal baby mice were infected with this organism, fatal infection occurred. In nude mice a chronic infection developed. Secondly, a rough, haemolytic strain was used to infect mice. In normal adult mice no multiplication of this strain was observed. This holds true also for DS-treated animals. In nude mice the bacteria were eliminated slowly. Normal baby mice could only be killed if the infective dose was increased. This strain was considered to be intermediate in virulence. The infection stimulated a considerable immune response in mice, although to a lesser degree than the smooth, haemolyticListeria strain. Thirdly, a smooth, non-haemolytic strain ofL. monocytogenes serovar 1/2a was used. The bacteria were rapidly eliminated in normal, in DS-treated and in nude animals. Normal baby mice did not develop fatal disease, so it was considered that this strain ofL. monocytogenes serovar 1/2a was avirulent. This variant was found to be non-immunogenic. A boosting of immunity of animals by this avirulentListeria strain was, however, found to be possible. A reasonable explanation for the rapid elimination of avirulentL. monocytogenes serovar 1/2 a from mice cannot be presented at this time. Whereas it is known that the macrophage system and the T-lymphocytes play an essential role in the resistance to virulentListeriae, there is no increased susceptibility of the avirulent bacteria to these defence mechanisms. Other bacterial properties, such as serum sensitivity and lysozyme susceptibility, are likewise considered to be unimportant.
TL;DR: The results indicate that—as long as the sodium gradient is normal—the axonal membrane functions as a barrier that largely prevents any outward movement of axoplasmic noradrenaline.
Abstract: The adrenergic nerve endings of the rat vas deferens were loaded with 3H-(−)-noradrenaline; COMT was inhibited by the presence of 10 μmol/l U-0521, and all experiments were carried out with calcium-free solution. After 100 min of wash-out a neuronal efflux of tritium was obtained which remained constant with time (when expressed as fractional rate of loss; FRL); it contained more DOPEG than noradrenaline. The in vitro administration of reserpine-like drugs (reserpine and Ro 4-1284) increased the FRL of tritium, presumably because of an increase in the leakage of noradrenaline from storage vesicles; the efflux of DOPEG increased more than that of noradrenaline, and the ratio NA/DOPEG declined. Inhibition of the membrane ATPase (by omission of potassium from the medium or by the presence of 3 mmol/l ouabain) increased the FRL of tritium, presumably because of an increase in the net leakage of noradrenaline from the storage vesicles (as a consequence of the fall in the concentration of free axoplasmic noradrenaline; see below). Veratridine also increased the FRL of tritium, partly because of its known reserpine-like effect (Bonisch et al. 1983); in the presence of 1 μmol/l veratridine, the efflux of DOPEG increased. Irrespective of the presence or absence of reserpine or Ro 4-1284, inhibition of the membrane ATPase or the presence of veratridine (agents or procedures which increase the axoplasmic sodium concentration) always resulted in a brisk increase of the efflux of noradrenaline that was accompanied by a simultaneous decrease in the efflux of DOPEG (see above for one exception). In all experiments the rise in internal sodium caused the ratio NA/DOPEG to increase. These results indicate that—as long as the sodium gradient is normal—the axonal membrane functions as a barrier that largely prevents any outward movement of axoplasmic noradrenaline. Consequently, the axoplasmic amine is largely deaminated, and the ratio NA/DOPEG is low. However, when the axoplasmic sodium concentration rises, axoplasmic noradrenaline is transported out of the nerve ending at such high rates that the axoplasmic noradrenaline concentration falls; the fall in the efflux of DOPEG is indicative of a fall in the intraneuronal formation of DOPEG. The results show that changes in the efflux of DOPEG (i.e., of a highly lipophilic metabolite that easily leaves adrenergic nerve endings) can serve as an index of changes in axoplasmic noradrenaline levels.
TL;DR: In this paper, the acrylate of (S)-ethyl lactate with cyclopentadiene proceed with diastereoface selectivity of up to 85:15 (non-catalyzed) and 93:7 (TiCl 4 -promoted) depending on the Lewis acid.
TL;DR: By using a homogeneous population of cells endowed with “uptake1”, it is possible to demonstrate — besides a pronounced lipophilic entry — a carrier-mediated uptake of 3H (+)-amphetamine.
Abstract: PC-12 cells (a clonal line of rat phaeochromocytoma cells) take up noradrenaline by a transport system which is identical with the neuronal amine transport system (“uptake1”). The uptake of 3H-noradrenaline into reserpine-pretreated PC-12 cells (monoamine oxidase inhibited) was saturable (Km=0.6±0.1 μmol/l), dependent on sodium and chloride, and competitively inhibited by (+)-amphetamine (Ki=0.18±0.04 μmol/l), cocaine (Ki=0.55±0.15 μmol/l) and desipramine (Ki=4.3±0.6 nmol/l). The uptake and accumulation of 3H (+)-amphetamine showed characteristics comparable to those of 3H-noradrenaline, since the uptake of 3H (+)-amphetamine (0.1 μmol/l) was reduced by omission of sodium or chloride from the incubation medium. The sodium-sensitive component of uptake and accumulation of 3H (+)-amphetamine was fully inhibited by cocaine and desipramine. The IC50 of desipramine for inhibition of the sodium-sensitive component of the 1-min uptake of 3H (+)-amphetamine (20 nmol/l) was about 2 nmol/l, i.e., identical with the Ki for inhibition of uptake of 3H-noradrenaline. At concentrations above 1 μmol/l, desipramine additionally caused an inhibition of the sodium-independent permeation of 3H (+)-amphetamine into PC-12 cells.
TL;DR: The surface coat staining is stronger and more widespread with solutions containing phosphate- instead of cacodylate-buffer; it is enhanced by section staining with lead citrate, and the cell surface coat stain does not traverse tight junctions nor permeate membranes.
Abstract: In aldehyde-fixed liver and renal cortex of rat and mouse several variations of postfixation with osmium tetroxide plus potassium ferrocyanide (FeII) were tried. Depending on the ferrocyanide concentration different staining patterns were observed in TEM.-Osmium-High Ferrocyanide [40 mM (∼1%) OsO4+36 mM (∼1.5%) FeII, pH 10.4], stains membranes and glycogen. Cytoplasmic ground substance, mitochondrial matrices and chromatin are partially extracted, cell surface coats remain unstained. Membrane contrast, but extraction too, are higher with solutions containing cacodylate- than phosphate-buffer.-Osmium-Low Ferrocyanide [40 mM (∼1%) OsO4+2 mM (∼0.08%) FeII, pH 7.4], stains cell surface coats and basal laminae, but not glycogen, except for special cases. The trilaminar structure of membranes is poorly delineated. Signs of cytoplasmic extraction are not visible. The surface coat staining is stronger and more widespread with solutions containing phosphate- instead of cacodylate-buffer; it is enhanced by section staining with lead citrate. The cell surface coat stain does not traverse tight junctions nor permeate membranes.