125I-endothelin-1 and 125I-big endothelin-1 in rat tissues: autoradiographic localization and receptor binding

Summary The potent vasoconstrictor peptide, endothelin-1 (ET-1), which exhibits a characteristically long-acting activity in vitro and in vivo, is thought to be generated in endothelial cells from a less active intermediate, big endothelin-1 (big ET-1). In addition to ET-1, big ET-1 is also present in the circulation. The autoradiographic localization of ¹²⁵I-big ET-1 and ¹²⁵I-ET-1 has been studied after intravenous administration in rat tissues. Highest enrichment of radioactivity was found in the kidney cortex for both peptides. Compared to blood levels, enrichment of radioactivity is also detected, in the vascular wall of the aorta. Comparing the radioactivity pattern of ET-1 and big ET-1, a nearly identical tissue distribution is observed, with the exception of the relative enrichment in the lung and the zona glomerulosa after administration of ET-1.Both radioligands show a specific and saturable binding to lung and kidney membranes. In the case of lung tissue, K _i values are 10^–10 M for endothelin-1 and 10^–8 M for big endothelin-1. This difference in affinities may account for the lack of binding of big endothelin-1 to lung tissue.     

QUANTITATIVE AND QUALITATIVE CHANGES IN RIBONUCLEIC ACIDS OF RAT BRAIN DEPENDENT ON AGE AND TRAINING EXPERIMENTS

—Investigations of rat brain RNA were carried out by phenol extraction of the whole brain and chromatographic fractionation into ribosomal RNA and transfer RNA. (1) The amounts of both RNA species increase in the course of the animal's development reaching a maximum at about the tenth week of life. The ratio of both species remains constant throughout the growth to the twentieth week. After the rats had been trained how to reach their forage by balancing on a stressed rope, the rRNA content was found to be significantly higher, whereas the tRNA content was unchanged. (2) The portion of ribosomes bound in polysome complexes decreases with increasing age of rats. Conditioning of the animals brings about again an increase in polysome content. It is supposed that this reflects an enhanced synthesis of specific proteins in young developing rats and in the course of conditioning. (3) In young rats a second valine specific tRNA could be found as a minor component in addition to the major valyl-tRNA. This additional component disappears as the animals advance to an age of 3 weeks and it could not be detected in the brains of rats after training experiments. In tRNAs specific for the amino acids leucine, lysine and phenylalanine no kind of deviation could be stated.     

Metabolic changes during substrate shifts in continuous cultures of the yeast Candida boidinii variant 60

Summary Substrate shift experiments in chemostat cultures with either methanol or glucose as carbon source were performed with the yeast Candida boidinii variant 60. At low dilution rates of 0.064 h^–1 the culture may be easily shifted from methanol to glucose medium and back again to methanol. From these experiments it can be seen that glucose does not give rise to any catabolite inhibition of alcohol oxidase. Alcohol oxidase and formaldehyde dehydrogenase seem to be regulated by a repression-derepression mechanism, as small basal activities of both these enzymes can still be measured during growth on glucose. On the other hand, formate dehydrogenase activity is completely absent in the presence of glucose. This kind of regulation seems to favor the smooth switch from growth on glucose to methanol metabolism.With methanol or glucose, growth yields (Y_S) of 0.3 and 0.35, respectively may be obtained, and oxygen consumption (Q_{O 2}) is much higher in methanol cultures than in glucose-grown cells. Accordingly, the RQ values during growth on methanol decrease to about 0.5. Based on the yield coefficient of 0.3, it is possible to calculate that 38% of the methanol consumed must be incorporated into biomass, whereas 62% of the methanol is oxidized to CO₂. The corresponding RQ of 0.56 could not be experimentally ascertained.The activities of three mitochondrial enzymes were found to be higher in methanol-grown cells than in cells from glucose cultures. The low activites of enzymes for the phosphogluconate route in methanol-grown cells indicates that a cyclic oxidation of formaldehyde via hexose phosphate to CO₂ cannot be of great importance for methanol metabolism.List of Symbols D 1/h Dilution rate - 1/h Specific growth rate - Q_{CO 2} mmol/g·h Specific CO₂ production rate - Q_{O 2} mmol/g·h Specific O₂ comsumption rate - Q_S g/g·h Specific substrate consumption rate - RQ ./. Respiratory quotient (Q_{CO 2}/Q_{O 2}) - S_O g/l Substrate concentration in the feeding medium - $#x0073;$#x0304 g/l Substrate concentration in the fermentor - $#x0078;$#x0304 g/l Biomass in the fermentor - Y_{O 2} g/mmol O₂ Biomass yield on oxygen - Y_S g/g Biomass yield on carbon source     

Purification and properties of an extracellular β-glucosidase from Lenzites trabea

Summary When culturing the cellulolytic-active Basidiomycete and brown-rot fungus Lenzites trabea A-419 in submerged culture with glucose and cellulose as a carbon source, the fungus only excreted -glucosidase (EC 3.2.1.21) and an endo-1,4--glucanase (EC 3.2.1.4).No evidence for C₁ activity (EC 3.2.1.91) was found in the culture filtrate or in the ultra concentrate. -Glucosidase could be separated from endoglucanase by chromatography on Sepharose 6-B. Further fractionation of the -glucosidase on DEAE-Sephadex A-25 resulted in a 525-fold purification. The molecular weight of the isolated -glucosidase was determined by co-chromatography on Sephadex G-200 to be 320,000 daltons. The enzyme developed maximum activities at pH 4.5 and 75°C. The enzyme does not act on crystalline cellulose or CMC, but it hydrolyzes cellotriose,-tetraose, and-pentaose to cellobiose and glucose. -glucosidase activity was strongly inhibited by the reaction product, glucose. A K_i value of 2.7×10^–3 (M) for noncompetitive inhibition was found.     

Purification and properties of an extracellular endo-1,4-β-glucanase fromLenzites trabea

An extracellular endo-1,4--glucanase (EC 3.2.1.4) has been isolated and purified from the culture solution of the basidiomyceteLenzites trabea grown on glucose and cellulose. Besides-glucosidase activity (EC 3.2.1.21) no evidence for C₁-activity (EC 3.2.1.91) in the culture solution was found.The endoglucanase has been purified in a four-step procedure including chromatography on Sepharose 6-B and DEAE-Sephadex A-50, adsorption on hydroxylapatite and gel filtration on Bio-Gel P-100. The enzyme showed maximum activity at pH 4.4 and 70°C. A molecular weight of 29000 Daltons was estimated by calibration on Bio-Gel P-100. The enzyme hydrolyses carboxymethyl cellulose (CMC) as well as xylan.List of Abbreviations CMC carboxymethyl cellulose - D.S. degree of substitution - D.P. degree of polymerisation - MW molecular weight     

Die photodynamische Wirkung von Thiopyronin auf Nucleinsäuren

Summary RNA and DNA in aqueous solutions were irradiated by a day light lamp in the presence of thiopyronin as a photosensitizer. Thereby especially guanine is photooxydized, adenine and uracil however are quite stable. The action spectrum of the photodynamic effect is in good agreement with the absorption spectrum of thiopyronin.DNA is modified by the photooxydation of guanine and thus, its enzymatic degradation in vitro is partly inhibited. In addition to the common deoxynucleoside-5-phosphates an oligonucleotide fraction is obtained by the action of pancreas deoxyribonuclease and snake venom phosphodiesterase, these oligonucleotides being resistant to further action of these enzymes. The results are quite similar to the resistance of ultraviolet-irradiated DNA to enzymatic degradation, on which we have reported earlier.Photodynamic inactivation of microorganisms may therefore be referred to the consequences of guanine destruction within the nucleic acids.

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Wir danken der Deutschen Forschungsgemeinschaft für die Unterstützung dieser Arbeit mit einer Sachbeihilfe.     

Die Bedeutung einiger anorganischer Komponenten des Seewassers für die Turgorregulation vonChaetomorpha linum (Cladophorales)

Zusammenfassung 1. Die negative Turgorregulation vonChaetomorpha linum nach Herabsetzung des Salzgehaltes im Außenmedium beruht in der Hauptsache auf einer Erniedrigung des osmotischen Potentials des Zellsaftes durch Abgabe von K^. und Cl.2. Während der positiven Turgorregulation nach Erhöhung des Salzgehaltes im Außenmedium konnte umgekehrt eine starke Speicherung von K^. und Cl beobachtet werden.3. Das Natrium als wichtigstes Kation des Seewassers ist für beide Prozesse osmotisch kaum von Bedeutung. Die Änderung des Natriumgehaltes im Versuchsmaterial betrug in beiden Fällen nur etwa 10% der Änderung seines Chloridwertes und nur etwa 5% der Änderung seines osmotischen Gesamtpotentials.4. Kalziummangel im Außenmedium führte zu einer starken Abgabe von KCl durch die Versuchspflanzen, welche dabei einen beträchtlichen Turgorverlust erlitten.5. Die ebenfalls durch Kalziummangel bewirkte starke Verquellung der Zellwände wird im Zusammenhang mit der sprughaften Abnahme des Kalziumgehaltes der Versuchspflanzen auf einen Ionenaustauschvorgang zurückgeführt, bei dem das Zellwand-Kalzium durch Natrium ersetzt werden dürfte.

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The importance of some inorganic components of sea water for the turgor-regulation ofChaetomorpha linum (Chladophorales)

Some algae of the intertidal zone are capable of regulating their turgor pressure. In 1896Drevs had already shown that this process is affected primarily by accumulation (positive turgor-regulation) or extrusion (negative turgor-regulation) of mineral salts and that transformation of stock material (e. g. starch) into osmotic active substances (e. g. sucrose) and vice versa plays no important role. His results are being confirmed by the present paper. InChaetomorpha linum (Müller)Kützing, lowering of salinity resulted in a significant release of potassium and chlorine (negative turgor-regulation). Changes in sodium content were only small. In algae exposed to a salinity of 30, the total sodium concentration was only about 10% that of the external medium. Salinity increase led to a marked accumulation (positive turgor-regulation) of potassium and chlorine. Even in this process sodium was engaged only to a small degree — despite its high concentration in the surrounding medium. In both cases internal changes in sodium content amounted only to about 5% of the total osmotic changes in the external medium. After transfer from 30 salinity into isosmotic artificial sea water without Ca^··, a rapid loss of potassium and chlorine was observed. The abrupt decrease of the calcium content accompanied by a marked swelling of cell walls, leading to a significant reduction of cell space, is interpreted as ion exchange process changing the cell wall Ca^.. against Na^..

     

Zellsaftgewinnung,AFS (apparent free space) und Vakuolenkonzentration der osmotisch wichtigsten mineralischen Bestandteile einiger Helgoländer Meeresalgen

Samples of cell sap in amounts suitable for chemical analysis of mineral compounds were obtained by high speed centrifugation of several frost-killed (-20° C) Helgoland algae under paraffin oil. In order to calculate the vacuole concentration of the mineral salts determined in these liquids, the extravacuolar solving space of the algae was measured as Lithium apparent free space (Li-AFS) after rinsing the algae for several minutes in balanced LiCl solutions. The Li-AFS was calculated from the results gained by flamephotometric determination of the Li-concentrations in the sap and in the bathing fluid. To avoid errors caused by interaction of Donnan-effects, the Li-AFS ofChaetomorpha linum kept in diluted sea water of different concentrations was measured. By plotting the results against the medium concentration, evidence was obtained to show that in 100 % Li-solution (corresponding osmotically to natural sea water of about 30 ‰), the Donnan effect was negligible. In the more diluted solutions, however, higher Li-AFS values were obtained. This would indicate that the differences in the distribution of Li-cations between medium and AFS, which are effected by the negative charges of indiffusible anions in the cytoplasm and of fixed acidic groups (e. g. R-COO^?) of phycocolloids in the wall material, will cause considerable errors if Li-concentrations are too low. Taking these experiences into account, AFS-values of several algae from Helgoland were measured by the same technique and the vacuole concentrations of the analysed mineral compounds calculated.