| | 41 | Author
| B. Schöbel, W. Pollmann | Requires cookie* | | | Title
| Isolation and Characterization of a Chlorogenic Acid Esterase from Aspergillus niger  | | | | Abstract
| The isolation and characterization o f a specific chlorogenic acid esterase is described. The en zyme activity is measured by determination of the hydrolysis product caffeic acid. The enzyme had been concentrated by means o f ultrafiltration and column-chromatography. The pH-and tempe rature optimum were 6.5 and 45 °C respectively. Divalent cations were not required for the en zyme activity. As other esterases, this enzyme is inhibited by di-isopropyl-phosphorofluoridate. TTie Ä Tm-value is 0.70 mM chlorogenic acid, the molecular weight 240000. The described enzyme is specific for chlorogenic acid. On the other hand a typical unspecific esterase like the pig liver esterases does not split chloro genic acid. The isoelectric focusing reveals several isoenzymes o f chlorogenase within a pl-range o f 4 .0 -4 .5 . | | | |
Reference
| Z. Naturforsch. 35c, 209 (1980); received November 20 1979/January 17 1980 | | | |
Published
| 1980 | | | |
Keywords
| Chlorogenic Acid Esterase, Aspergillus niger, High Performance Thin Layer Chromatography | | | |
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| default:Reihe_C/35/ZNC-1980-35c-0209.pdf | | | | Identifier
| ZNC-1980-35c-0209 | | | | Volume
| 35 | |
| 42 | Author
| Heinz-W Alter, Scheid, Adelheid Ehmke, Thomas Hartm | Requires cookie* | | | Title
| Plant NAD-Dependent Glutamate Dehydrogenase. Purification, Molecular Properties and Metal Ion Activation of the Enzymes from Lemna minor and Pisum sativum | | | | Abstract
| Glutamate dehydrogenase (L-glutamate: N A D + oxidoreductase (deaminating) EC 1.4.1.2) has been purified to homogeneity from Lemna minor and seeds o f Pisum sativum. As established by polyacrylamide gel electrophoresis the Pisum-enzyme constitutes a multiple pattern o f seven char ge isoenzymes whereas the Lemna enzyme shows one single protein band. Molecular weights of 230 000 were calculated for both enzymes by sedimentation equilibrium measurements (Pisum-enzyme]I and comparative gel filtration (Lemna-enzyme). Sodium dodecyl sulfate gel electropho resis and electron microscopic observations revealed that both enzymes are composed of four identical subunits (molecular weight 58 500) arranged in a tetraedric structure. The amino acid compositions of both enzymes are similar to those of various hexameric glutamate dehydrogen ases. The N-terminal amino acid of the Pisum-enzyme is alanine. Both enzymes require Ca2+ for maximal catalytic activity. For the Lemna-enzyme the K0.s values for Ca2+ are 22 /j.m (NADH-de-pendent reaction) and 4 piM (N A D +-dependent reaction), respectively. Ca2+ which to some extent can be replaced by Zn2+ does not affect the enzyme aggregation but seems to govern a reversible equilibrium between catalytically active and inactive enzyme forms. | | | |
Reference
| Z. Naturforsch. 35c, 213—221 (1980); received November 21 1979 | | | |
Published
| 1980 | | | |
Keywords
| Lemna minor, Pisum sativum, Glutamate Dehydrogenase, Purification, Molecular Properties, Me tal Ion Activation | | | |
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| default:Reihe_C/35/ZNC-1980-35c-0213.pdf | | | | Identifier
| ZNC-1980-35c-0213 | | | | Volume
| 35 | |
| 43 | Author
| Klaus Müller, Rainer Jaenicke | Requires cookie* | | | Title
| Denaturation and Rcnaturation of Bovine Liver Glutamic Dehydrogenase after Dissociation in Various Denaturants | | | | Abstract
| Denaturation, Renaturation, Glutamic Dehydrogenase Oligomeric glutamic dehydrogenase from bovine liver is dissociated to inactive monomers (M r = 56 000) under a wide variety o f conditions: 3 > pH > 12, 6 m guanidine • HC1, 6 M urea, 0.2% sodium dodecylsulfate. High hydrostatic pressure (< 1 kbar) only affects the association equi librium of the native hexamer to higher polymers. The respective reaction volume (A V = 28 + 5 ml • mol-1 at 298 K, 1 bar) is linearly dependent on temperature and pressure. At p > 1.5 kbar dissociation of the hexamer occurs; this reaction is accompanied by irreversible deactivation. Depending on the denaturant applied for the monomerization, the final conformational state o f the polypeptide chain differs widely regarding its residual structure. As taken from laser light scattering measurements the rate o f dissociation at pH 1.8 follows first order kinetics with a rate constant = 0.42 + 0.06 s-1. In the range of the oligomer ^ monomer transition, dissociation is accompanied by irreversible aggregation leading to inactive high molecular weight material. At low concentration (c < 5ng/m l) this side reaction can be slowed down, so that the reconstitution o f the enzyme can be monitored using spectroscopic techniques. Concentration dependent stopped-flow experiments prove the re gain of fluorescence to be a rapid first order process; the respective half-times at pH 7.4 are ti/2 = 2.0 + 0.5 ms and 0.7 ± 0.2 ms for the "renaturation" from 6 M guanidine • HC1, pH 6 , and pH ~ 2, respectively. The product o f reconstitution shows the fluorescence and circular dichroism pattern character istic for the native enzyme. However, no reactivation can be achieved under any o f the following conditions: optimum protection against chemical modification; variation of enzyme concentra tion, temperature, and hydrostatic pressure; addition of specific ligands such as coenzymes, sub strates, ADP, membrane constituents (cardiolipin, electron transfer particles ETPH). Obviously, the "renaturation" (D -*■ N) of glutamic dehydrogenase is governed by a side reaction according to N ->D ^R -^A which causes aggregation o f intermediates R instead o f reconstitution of the native enzyme. | | | |
Reference
| Z. Naturforsch. 35c, 222—228 (1980); received December 28 1979 | | | |
Published
| 1980 | | | |
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| default:Reihe_C/35/ZNC-1980-35c-0222.pdf | | | | Identifier
| ZNC-1980-35c-0222 | | | | Volume
| 35 | |
| 44 | Author
| Cornelia Pfleiderer, Jobst-H Einrich Klemme | Requires cookie* | | | Title
| Pyrophosphat-abhängige D-Fructose-6-phosphat Phosphotransferase in Rhodospirillaceae Pyrophosphate-Dependent D-Fructose-6-phosphate-Phosphotransferase in Rhodospirillaceae | | | | Abstract
| Fructose-6 -phosphate Phosphotransferase, Pyrophosphate, Rhodospirillaceae A pyrophosphate-dependent fructose-6 -phosphate phosphotransferase from the photosynthetic bacterium Rhodospirillum rubrum was partially purified and characterized in respect to kinetic and regulatory properties. The enzyme had a molecular weight o f about 95 000 dal ton and requir ed Mg2+-ions for catalysis and maintenance o f activity. The phosphotransferase was specific for fructose-6 -phosphate (F-6 -P) and inorganic pyrophosphate (PP) as substrates o f the fructose-1,6 -bisphosphate-forming reaction (forward reaction). In the phosphate (PO-dependent back reaction, the preferred substrate was fructose-1,6-bisphosphate (FBP). At optimal pH (7.2 for the forward, and 8 . 6 for the back reaction) the back reaction had a slightly higher vmax than the forward reac tion. The substrate-saturation curves of the enzyme were all hyperbolic with intersecting kinetic pattern. The A^m-values (in mM) at saturating MgCl2-concentration were: 0.38 (F-6 -P); 0.025 (PP); 0.02 (FBP) and 0.82 (Pi). The forward reaction was inhibited by ADP and AMP. The inhibition by ADP (Kj = 0.18 mM) was o f the mixed type in respect to F-6 -P, but independent of the PP-con-centration. The inhibition by AMP (K s = 0.017 mM) was o f a more complex type, because AMP not only decreased the vmax o f the F-6 -P-or PP-saturation curve, but also increased the Hill-coef-ficient from «H = 1 to nH = 2.5 of the F-6 -P-saturation curve. The inhibition of the back reaction by the two adenylates was less pronounced. ATP (at 2.5 mM), like citrate, inhibited the back reaction only at low MgCl2 concentration (1 mM) indicating that the inhibitory effect was due to the chela tion of Mg2+. Out of 5 other species of the Rhodospirillaceae tested, the PP-dependent phospho-fructokinase was only shown to be present in Rhodopseudomonas gelatinosa. | | | |
Reference
| Z. Naturforsch. 35c, 229—238 (1980); eingegangen am 20. November 1979 | | | |
Published
| 1980 | | | |
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| default:Reihe_C/35/ZNC-1980-35c-0229.pdf | | | | Identifier
| ZNC-1980-35c-0229 | | | | Volume
| 35 | |
| 45 | Author
| GünterF. Wildner, PrafullachandraV. Sane, Jürgen Henkel | Requires cookie* | | | Title
| The Activation of Ribulose-l,5-bisphosphate Carboxylase-Oxygenase from Spinach by Oxygen Changes of the Enzyme Conformation during Air-Argon Transitions | | | | Abstract
| The effect of oxygen on ribulose-l,5-bisphosphate carboxylase-oxygenase from spinach was in vestigated. Both activities were deactivated by removal of oxygen and reversibly reactivated by oxygenation of the enzyme solution. The change in enzyme activities was accompanied by confor mational changes as studied by the use of intrinsic and extrinsic fluorescent probes. The analysis of cysteine sulfhydryl groups accessible to 5,5'-dithiobis-(2-nitrobenzoic acid) re vealed that the number of these groups changed with the oxygen concentration. The kinetic of the exposure of eight cysteine residues was similar to the loss of enzyme activities. The modification of these groups with 5,5'-dithiobis-(2-nitrobenzoic acid) caused almost complete loss of both the activities. The enzyme isolated from a photolithotrophic organism, Chromatium vinosum, was not affected by oxygen removal. During air — argon transitions, neither the enzyme conformation nor the num ber of accessible sulfhydryl groups changed. | | | |
Reference
| Z. Naturforsch. 35c, 239—248 (1980); received December 12 1979 | | | |
Published
| 1980 | | | |
Keywords
| Ribulose-l, 5-bisphosphate Carboxylase, Ribulose-l, 5-bisphosphate Oxygenase, Enzyme Confor mation, Oxygen Effect, Photosynthesis | | | |
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| default:Reihe_C/35/ZNC-1980-35c-0239.pdf | | | | Identifier
| ZNC-1980-35c-0239 | | | | Volume
| 35 | |
| 46 | Author
| John Kamsteega, Jan Van Brederode, Gerrit Van Nigtevecht | Requires cookie* | | | Title
| Campion (Silene dioica) | | | | Abstract
| An enzyme catalyzing the transfer of the rhamnosyl moiety of UDP-L-rhamnose to the 6 -hydro-xyl group of the 3-O-bound glucose of anthocyanidin 3-O-glucosides has been demonstrated in petal extracts of Silene dioica plants. The enzyme activity is controlled by a single dominant gene N\ no rhamnosyltransferase activity is found in petals of n/n plants. The 60-fold purified rhamno-syltransferase exhibits a pH optimum of 8.1, has a molecular weight of about 45000 daltons, is sti mulated by the divalent metal ions Mg2+, Mn2+ and Co2+, and has a "true Km" value of 0.09 mM for UDP-L-rhamnose and 2.2 mM for cyanidin 3-O-glucoside. Pelargonidin 3-O-glucoside and delphinidin 3-O-glucoside can also serve as acceptor. The enzyme can also catalyze the rhamnosy-lation of anthocyanidin 3,5-diglucosides although at reduced rate. The biosynthetic pathway for the synthesis of cyanidin 3-rhamnosylglucoside-5-glucoside in petals of S. dioica is discussed. | | | |
Reference
| Z. Naturforsch. 35c, 249—257 (1980); received October 22 1979 | | | |
Published
| 1980 | | | |
Keywords
| Silene dioica, Caryophyllaceae, Anthocyanin Biosynthesis, Cyanidin-, Pelargonidin-glycosides, Glycosyltransferases, Genetic Control | | | |
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| default:Reihe_C/35/ZNC-1980-35c-0249.pdf | | | | Identifier
| ZNC-1980-35c-0249 | | | | Volume
| 35 | |
| 47 | Author
| A.Martin Gonzalez, M. T. Izquierdo | Requires cookie* | | | Title
| Effects of an Electric Field of Sinusoidal Waves on the Amino Acid Biosynthesis by Azotobacter | | | | Abstract
| Azotobacter vinelandii, Amino Acids, Electric Field Electric fields of sinusoidal waves have been applied in cultures of Azotobacter vinelandii, with potentials between 0 V and 10 V, intensities from 0 mA to 16 mA and frequencies between 5 Hz and 200 KHz. The influence of the electric field of sinusoidal waves on the nitrogen fixation on the post culture medium composition has a maximum at 5 V, 8 mA and 20 Hz. The rate of synthesis of specific amino acids by Azotobacter depends on the frequency and potential of the electric field applied. The concentration of each amino acid present in the post-culture medium is increased according to the electric field employed and the amino acid biosynthesis in culture medium is activated during the first days of incubation. | | | |
Reference
| Z. Naturforsch. 35c, 258—261 (1980); received March 5/September 21 1979 | | | |
Published
| 1980 | | | |
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| default:Reihe_C/35/ZNC-1980-35c-0258.pdf | | | | Identifier
| ZNC-1980-35c-0258 | | | | Volume
| 35 | |
| 48 | Author
| F.C M Dnessens, R.M H Verbeeck | Requires cookie* | | | Title
| Evidence for Intermediate Metastable States during Equilibration of Bone and Dental Tissues | | | | Abstract
| Experimental data were collected on the solubility equilibrium of the mineral of bone, tooth enamel and calcium phosphate renal stones. Evaluation in the form of potential diagrams of Ca(OH) 2 versus H3P 0 4 shows that Ca/P ratios of 1, 4/3, 10/7, 3/2 and 5/3, related to phases like brushite, octocalcium phosphate, whitlockite, defective apatite and hydroxyapatite respectively can be important. These facts allow the interpretation that many of these calcium phosphates are present simultaneously in biominerals or that they are formed during the equilibration. | | | |
Reference
| Z. Naturforsch. 35c, 262 (1980); received December 27 1979 | | | |
Published
| 1980 | | | |
Keywords
| Calcium Phosphates, Solubility, Bone, Dental Enamel | | | |
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| default:Reihe_C/35/ZNC-1980-35c-0262.pdf | | | | Identifier
| ZNC-1980-35c-0262 | | | | Volume
| 35 | |
| 50 | Author
| Wilfried Meyer, Hartmut Follmann | Requires cookie* | | | Title
| A Study of the Substrate and Inhibitor Specificities of AM P Aminohydrolase, 5'-Nucleotidase, and Adenylate Kinase with Adenosine Carboxylates of Variable Chain Length | | | | Abstract
| Adenosine 5'-Uronic Acid, 5'-Deoxyadenosine 5'-Carboxylic Acids, Enzyme Kinetics, Molecular Conformations, Nucleotide Antagonists A series of AMP analogs in which a terminal carboxylate residue, linked to C4' of the ribose moiety of adenosine by zero, one, or two methylene groups (1, 2 ,3) or by the unsaturated ethyli-dene link (4) replaces the phosphate anion, is tested for activity as substrates or effectors of three enzymes known to interact with AMP with a different degree of specificity. 2 —4 are substrates of AMP aminohydrolase, 3 and 4 are competitive inhibitors of adenylate kinase, and all acids produce competitive inhibition of the least specific enzyme, 5'-nucleotidase. These activities can be cor related with the intramolecular flexibility of anionic substituent and adenine base which in turn is expressed in typical shifts of the proton magnetic resonance signal of purine H-8. The uronic acid 1, having a rigid molecular conformation, is inactive towards two AMP-dependent enzymes and little active with the third, indicating that this type of compound is not suitable as a nucleotide an tagonist whereas nucleoside carboxylates of type 2 and 3 have a higher potential as effectors of nucleotide metabolism. | | | |
Reference
| Z. Naturforsch. 35c, 273—2 (1980); received December 5 1979 | | | |
Published
| 1980 | | | |
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| default:Reihe_C/35/ZNC-1980-35c-0273.pdf | | | | Identifier
| ZNC-1980-35c-0273 | | | | Volume
| 35 | |
| 51 | Author
| S. I. Ahmad | Requires cookie* | | | Title
| Escherichia coli K12 | | | | Abstract
| When grown in thymine-free minimal synthetic medium, thy A recA mutants of Escherichia coli K\2 were comparatively more resistant and thy A recBC mutants more sensitive to thymineless death (TLD) than their respective parent strains. No excessive numbers of single-strand breaks were observed in the DNA of the recBC mutant strain starved for thymine, hence the hypersensi tivity for TLD in this strain was not caused by this type of DNA damage. Although experiments were performed with the same recBC mutant strain as used by earlier workers, results presented here contradict earlier findings that recBC mutants are no more sensitive and recA mutants are no more resistant to TLD. | | | |
Reference
| Z. Naturforsch. 35c, 279 (1980); received November 5 1979 | | | |
Published
| 1980 | | | |
Keywords
| RecA, RecBC, Thymineless Death, Ecoli | | | |
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| default:Reihe_C/35/ZNC-1980-35c-0279.pdf | | | | Identifier
| ZNC-1980-35c-0279 | | | | Volume
| 35 | |
| 52 | Author
| Volker Kinzel, James Richards | Requires cookie* | | | Title
| Culture Density and Age-Dependent Interactions of 3 T 3 and SV 3T 3 Cells with Immobilized and Soluble Lens Culinaris Lectin | | | | Abstract
| Short term binding of both Balb/c derived 3T 3 cells and SV 3T3 cells to 2B-Sepharose coated with Lens culinaris lectin (LCL) was compared with their LCL-induced agglutinability in relation to culture density and age. The cells were grown for 4 days either to low (LD) or to high density (HD); for certain experiments HD-cells were stimulated (HDS) by a short trypsin treatment and/ or by addition of fresh medium. HD-3T3 cells bound somewhat faster to immobilized LCL than LD -3T3 cells, although LD -3T3 cells agglutinated at lower LCL concentrations. In the case of SV 3T3 cells, binding was much less pronounced for HD than for LD cells. The agglutinability of HD-SV3T3 cells, however, was greater than that of the other transformed groups. Upon stimula tion, binding and agglutinability data of both HD cell lines began to resemble the results obtained with LD-cells. Taken together, the data revealed in all cases an inverse relationship between bind ing and agglutinability, i. e., high agglutinability was closely correlated with slower binding and vice versa. The results indicate that culture density and age-dependent differences in cell surface architecture can be detected by short term binding to immobilized LCL. | | | |
Reference
| Z. Naturforsch. 35c, 284—2 (1980); received August 24/November 22 1979 | | | |
Published
| 1980 | | | |
Keywords
| Mouse Fibroblasts, Density Dependence, Cell Surface, Immobilized Lectin, Lens Culinaris Lectin | | | |
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| default:Reihe_C/35/ZNC-1980-35c-0284.pdf | | | | Identifier
| ZNC-1980-35c-0284 | | | | Volume
| 35 | |
| 53 | Author
| P. V. Sane, T. S. Desai, V. G. Tatake | Requires cookie* | | | Title
| Luminescence from Photosystem I at High Temperatures | | | | Abstract
| The changes in the fluorescence and delayed fluorescence intensity of spinach leaf as affected by temperature were studied. It was observed that the delayed fluorescence showed a maximum at about 45 °C whereas the fluorescence maximum was at about 55 °C. An examination of the emission spectra of delayed fluorescence at different temperatures showed that at higher tem peratures the relative emission at 735 nm was increased. It is argued that at higher temperatures the luminescence from photosystem I contributes to delayed fluorescence. | | | |
Reference
| Z. Naturforsch. 35c, 289—292 (1980); received November 1 1979 | | | |
Published
| 1980 | | | |
Keywords
| Fluorescence, Delayed Fluorescence, Photosystem I | | | |
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| default:Reihe_C/35/ZNC-1980-35c-0289.pdf | | | | Identifier
| ZNC-1980-35c-0289 | | | | Volume
| 35 | |
| 54 | Author
| P. V. Sane, Udo Johanningmeier | Requires cookie* | | | Title
| Inhibition by Tetranitromethane of Photosynthetic Electron Transport from W ater to Photosystem II in Chloroplasts | | | | Abstract
| Tetranitromethane, Inhibition of Photosynthesis, Oxygen Evolution, Photosystem II Low concentrations (10 /xM) of tetranitromethane inhibit noncyclic electron transport in spinach chloroplasts. A study of different partial electron transport reactions shows that tetranitromethane primarily interferes with the electron flow from water to PS II. At higher concentrations the oxida tion of plastohydroquinone is also inhibited. Because diphenyl carbazide but not Mn2+ ions can donate electrons efficiently to PS II in the presence of tetranitromethane it is suggested that it blocks the donor side of PS II prior to donation of electrons by diphenyl carbazide. The pH de pendence of the inhibition by this protein modifying reagent may indicate that a functional-SH group is essential for a protein, which mediates electron transport between the water splitting complex and the reaction center of PS II. | | | |
Reference
| Z. Naturforsch. 35c, 293—297 (1980); received November 26 1979 | | | |
Published
| 1980 | | | |
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| default:Reihe_C/35/ZNC-1980-35c-0293.pdf | | | | Identifier
| ZNC-1980-35c-0293 | | | | Volume
| 35 | |
| 55 | Author
| Eckhard Loos, Ernst Kellner | Requires cookie* | | | Title
| Influence of Magnesium Ions on the Action of Photosystems I and II at Different Wavelengths Experiments with Barley Chloroplasts of Different Chlorophyll b Content | | | | Abstract
| Barley leaves grown under a natural light/dark regime have a chlorophyll content o f 1300 [ig/g fresh weight and a chlorophyll a /b ratio of 2 .5 -3 . W hen the plants are grown under cycles of 2 min lig h t/1 18 min dark, the respective values are 50 and 5 — 9. W ith chloroplasts with low chlo rophyll b content variable fluorescence is depressed by about 30% by MgCl2; with those o f high chlorophyll b content a threefold increase is seen instead. Action spectra for variable fluorescence o f chloroplasts o f high chlorophylll b content show enhancement by Mg2+ around 475 and 650 nm; for the system I-mediated methyl viologen reduction, a depression is seen at these wavelengths. These effects are practically absent in chloroplasts with low chlorophyll b content. The data corro borate the hypothesis that a chlorophyll b-containing pigment protein complex is required for re gulation of energy transfer to system I and II by magnesium ions. | | | |
Reference
| Z. Naturforsch. 35c, 298—302 (1980); received October 17 1979/January 23 1980 | | | |
Published
| 1980 | | | |
Keywords
| Chlorophyll b, Barley, Magnesium Ions, Wavelength Action | | | |
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| default:Reihe_C/35/ZNC-1980-35c-0298.pdf | | | | Identifier
| ZNC-1980-35c-0298 | | | | Volume
| 35 | |
| 56 | Author
| E. F. Elstner, E. Lengfelder, G. Kwiatkowski | Requires cookie* | | | Title
| Paraquat-Catalyzed Photodestructions in Subchloroplast Particles are Independent on Photosynthetic Electron Transport | | | | Abstract
| Light dependent ethane form ation and chlorophyll bleaching in isolated chloroplast lamellae are enhanced by either methylviologen or a-linolenic acid. Both ethane formation and chloro phyll bleaching are also enhanced in chloroplast particles deficient in photosynthetic electron transport, e. g. after aging, heat treatm ent or digitonin fragmentation. Ethane form ation by sub chloroplast particles from endogenous substrates in the presence of methylviologen is inhibited by superoxide dism utase or by a penicillam ine copper complex exhibiting superoxide dismutase activity whereas chlorophyll bleaching is enhanced by superoxide dismutase — active substances. Maximal rates o f ethane form ation in subchloroplast particles are observed when more than 50% of the chlorophyll is bleached and continues after 98% chlorophyll bleaching. This result indi cated that methylviologen -stim ulated ethane production in subchloroplast particles is not de pendent on photosynthetic electron transport but involves "activated oxygen" — species like the superoxide radical ion, generated by a light receptor derived from the pigmentsystem o f photo system I or activated after its destruction. | | | |
Reference
| Z. Naturforsch. 35c, 303—307 (1980); received D ecem ber 12 1979 | | | |
Published
| 1980 | | | |
Keywords
| Ethane Form ation, Chlorophyll Bleaching, Oxygen Radicals, Fatty Acid Peroxidation | | | |
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| default:Reihe_C/35/ZNC-1980-35c-0303.pdf | | | | Identifier
| ZNC-1980-35c-0303 | | | | Volume
| 35 | |
| 57 | Author
| H. Stieve, I. Claßen-Linke | Requires cookie* | | | Title
| The Effect of Changed Extracellular Calcium and Sodium Concentration on the Electroretinogram of the Crayfish Retina | | | | Abstract
| Astacus Retina, Electroretinogram, Extracellular Calcium and Sodium Concentration The electroretinogram (ERG) o f the isolated retina of the crayfish Astacus leptodactylus evoked by strong 10 ms light flashes at constant 5 min intervals was measured while the retina was con tinuously superfused with various salines which differed in Ca2+-and Na^concentrations. The os motic pressure o f test-and reference-saline was adjusted to be identical by adding sucrose. Results: 1. Upon raising the calcium-concentration of the superfusate in the range of 20—150 mmol/1 (constant N a+-concentration: 208 mmol/1) the peak amplitude Amax and the half time of decay t2 of the ERG both decrease gradually up to about 50% in respect to the corresponding value in refer ence saline. 2. The recovery o f the ERG due to dark adaptation following the "weakly light adapted state" is greatly diminished in high external [Ca2+]ex-3. Lowering the external calcium-concentration (10 -* • 1 mmol/1) causes a small increase in hmsix and a strong increase of the half time o f decay t2 (about 180%). Upon lowering the calcium concentration of the superfusate to about 1 nmol/1 by 1 mmol/1 of the calcium buffer EDTA, a slowly augmenting diminution o f the ERG height hm SLX occurs. How ever, a strong retardation of the falling phase o f the ERG characterized by an increase in t2 occurs quickly. Even after 90 min stay in the low calcium saline the retina is still not inexcitable; hm iLX is 5 — 10% of the reference value. The diminution of hmax occurs about six-fold faster when the buf fer concentration is raised to 10 mmol/1 EDTA. 4. Additional lowering o f the N a+-concentration (208 — ► 20.8 mmol/1) in a superfusate with a calcium concentration raised to 150 mmol/1 causes a strong reduction of the ERG amplitude /?max to about 10%. 5. In a superfusate containing 1 nmol/1 calcium such lowering o f the sodium concentration (208 -*■ 20.8 mmol/1) causes a diminution of the ERG height to about 40% and the shape o f the ERG to become polyphasic; at least two maxima with different time to peak values are observed. Interpretation: 1. The similarity of effects, namely raising external calcium concentration and light adaptation on the one hand and lowering external calcium and dark adaptation on the other hand may indi cate that the external calcium is acting on the adaptation mechanism o f the photoreceptor cells, presumably by influencing the intracellular [Ca2+], 2. The great tolerance o f the retina against Ca2+-deficiency in the superfusate might be effected by calcium stores in the retina which need high Ca2+-buffer concentrations in the superfusate to become exhausted. 3. In contrast to the Limulus ventral nerve photoreceptor there does not seem to be an antagonis tic effect of sodium and calcium in the crayfish retina on the control o f the light channels. 4. The crayfish receptor potential seems to be composed of at least two different processes. Lowering calcium-and lowering external sodium-concentration both diminish the height and change the time course of the two components to a different degree. This could be caused by in fluencing the state of adaptation and thereby making the two maxima separately visible. | | | |
Reference
| Z. Naturforsch. 35c, 308—318 (1980); received December 17 1979 | | | |
Published
| 1980 | | | |
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| default:Reihe_C/35/ZNC-1980-35c-0308.pdf | | | | Identifier
| ZNC-1980-35c-0308 | | | | Volume
| 35 | |
| 58 | Author
| L. A. Buscarlet, A. Ferran, M. Larroque | Requires cookie* | | | Title
| Water Budget in Larvae of Semiadalia undecimnotata Schn. Studied with Tritiated Water | | | | Abstract
| The rates of water vapor entry, body water clearance and the net loss of water in larvae o f Semi adalia undecimnotata (3rd and 4th stage) of different weights were determ ined from observed changes in the mass of body water and its tritium content for each of several relative hum idities (RH) in am bient air. The water clearance and vapor entry rates as a function o f weight increases from emergence to the middle of the stage and then rem ains constant. The vapor entry rate increases with RH while the clearance rate is independant o f RH. The perm eability of the cuticle has not the same value in the inward and in the outward direction. The perm eability to body water escape is not affected by RH and reaches a m axim um at the m iddle of the stage. The inward perm eability does not depend on weight and increases appreciably as RH reaches saturation. One day of starvation affected these movements o f water most in larvae at the m iddle o f their stage. These results are discussed in relation to some physiological data concerning the cuticular struc ture and its evolution with age. | | | |
Reference
| Z. Naturforsch. 35c, 319—325 (1980); received N ovem ber 1 1979 | | | |
Published
| 1980 | | | |
Keywords
| Semiadalia undecimnotata, Tritiated Water, Transpiration, Water Absorption, Cuticle Permeability | | | |
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| default:Reihe_C/35/ZNC-1980-35c-0319.pdf | | | | Identifier
| ZNC-1980-35c-0319 | | | | Volume
| 35 | |
| 59 | Author
| Rolf Wüst, Trygve Kolberg, Alvaro Palma, Alfredo Palma | Requires cookie* | | | Title
| A Hydrodynamic Model of Cerebrospinal Fluid Flow in Man | | | | Abstract
| A hydrodynamic bi-compartmental model for the cerebrospinal fluid (CSF) flow in hum ans is presented which combines anatomical and physiological conditions in the central nervous system with results of special radioisotope diagnostic techniques. N orm al and disturbed conditions, the diagnostic methods and the results are explained. A differential equation for the time behaviour of regional radioisotope concentrations is derived by applying to the model m athem atical procedures which are fam iliar from the description o f radioactive decay series, or reaction kinetics of chemical or pharmaceutical processes. The solutions are analysed and discussed with respect to findings o f isotope diagnostics, and param eters for the com plete and quantitative evaluation of CSF flow systems are derived. A system factor is introduced for classification purposes and, in conjunction with basic principles o f hydrodynam ics, is used to postulate a similarity law of CSF flow systems. The diagnostical and therapeutical value of the model for analysis and simulation of CSF flow systems is discussed. Practical applications to other disciplines are proposed. | | | |
Reference
| Z. Naturforsch. 35c, 326—339 (1980); received January 16 1978/September 24 1979 | | | |
Published
| 1980 | | | |
Keywords
| Cerebrospinal Fluid Dynamics, Hydrodynamic Bi-Com partm ental Model, M athem atical Analysis, Cerebrospinal Fluid Flow Parameters, Radioisotope Serial Scanning | | | |
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| default:Reihe_C/35/ZNC-1980-35c-0326.pdf | | | | Identifier
| ZNC-1980-35c-0326 | | | | Volume
| 35 | |
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