Showing papers by "University of Freiburg published in 1975"

Isoenzymes of p-coumarate: CoA ligase from cell suspension cultures of Glycine max.

Abstract: Two isoenzymes of p-coumarate: CoA ligase were isolated from cell suspension cultures of soybean (Glycine max L., var. Mandarin). Separation and partial purification of the enzymes were achieved by precipitation with MnCl2 and (NH4)2SO4, and column chromatography on DEAE-cellulose, Sephadex G-100 and hydroxyapatite. The isoenzymes had approximately the same molecular weight, but differed significantly with respect to their substrate specificity, their inhibition constants for AMP, their dependence on pH and ionic strength for optimum activity, and their fractionation pattern during the purification procedure or upon analytical disc-gel electrophoresis. Both coumarate: CoA ligases were specific for the activation of various substituted cinnamic acids. Of the cinnamic acids tested, ferulic, sinapic, 5-hydroxyferulic, p-coumaric, and caffeic acids were the substrates with the lowest apparent Km values (on all the order of 1 to 4 x 10(-5) M) for isoenzyme 1. The lowest apparent Km values (from about 1 to 9 x 10(-5) M) for isoenzyme 2 were obtained for caffeic, p-coumaric, m-coumaric, and o-coumaric acids. Sinapic acid and several methoxycinnamic acids were efficient substrates of isoenzyme 1 but were not activated at all by isoenzyme 2. The possible roles of the two p-coumarate: CoA ligase isoenzymes in the phenylpropanoid metabolism of the cell cultures are discussed.

Genetics of alcohol dehydrogenase in Saccharomyces cerevisiae: I. Isolation and genetic analysis of adh mutants

Abstract: On the basis of allyalcohol resistance, Saccharomyces cerevisiae mutanta were isolated that were deficient in alcohol dehydrogenase (ADH). The mutants were divided into three classes by their different ADH isozyme pattern obtained after starch-gel electrophoresis: adc mutants that did not produce the constitutive ADH, adr mutants from which the glucose repressible enzyme (ADHII) was absent, and adm mutants deficient in ADH activity associated with the mitochondria. Genetic analysis showed that two genes control synthesis of the glucose repressible enzyme ADHII, one gene the constitutive ADHI and a fourth nuclear gene the mitochondrial ADH. None of these four genes showed any linkage. The various mutant types did not show drastic effects on yeast growth on media containing glucose or ethanol as sole carbon sources.

A new approach to explain the “high irradiance responses” of photomorphogenesis on the basis of phytochrome

Abstract: A new approach to explain the “high irradiance responses” of photomorphogenesis on the basis of phytochrome is described. Irradiance and wave-length dependency of different phytochrome reaction models are analyzed. 1) An open phytochrome model which is based on spectophotometric data (Schafer, 1972; Schafer et al., 1972; Schafer and Mohr, 1974) and describes only the induction phenomena is presented; 2) A closed phytochrome-receptor model which is based on the analysis of phytochrome-receptor interactions (Quail et al., 1973a. Quail and Schafer, 1974) describes the principal behavior of high irradiance responses, namely, optimum quantum responsivity in the far-red and blue part of the visible spectrum and the irradiance dependency. This model cannot account for the induction phenomena; 3) An open phytochrome-receptor model which describes both the properties of the induction responses, as well as those of the high irradiance responses, is tested for its physiological relevance by comparing the predictions based on this model with the measured data for phytochrome controlled anthocyanin synthesis (Wagner and Mohr, 1966) and suppression of lipoxygenase synthesis in the mustard seedling (Oelze and Mohr, 1973).

Enzymic synthesis of an aromatic ring from acetate units. Partial purification and some properties of flavanone synthase from cell-suspension cultures of Petroselinum hortense.

Abstract: Flavanone synthase was isolated and purified about 300-fold from fermenter-grown, light-induced cell suspension cultures of Petroselinum hortense. The enzyme catalyzed the formation of the flavanone naringenin from p-coumaroyl-CoA and malonyl-CoA. Trapping experiments with an enzyme preparation, which was free of chalcone isomerase activity, revealed that in fact the flavanone and not the isomeric chalcone was the immediate product of the synthase reaction. Thus the enzyme is not a chalcone synthase as previously assumed. No cofactors were required for flavanone synthase activity. The enzyme was strongly inhibited by the two reaction products naringenin and CoASH, by the antibiotic cerulenin, by acetyl-CoA, and by several compounds reacting with sulfhydryl groups. Optimal enzyme activity was found at pH 8.0, at 30°C, and at an ionic strength of 0.1–0.3 M potassium phosphate. EDTA, Mg2+, Ca2+, or Fe2+ at concentrations of about 0.7 μM did not affect the enzyme activity. Apparent molecular weights of approx. 120000, 50000, and 70000, respectively, were determined for flavanone synthase and two metabolically related enzymes, chalcone isomerase and malonyl-CoA : flavonoid glycoside malonyl transferase. The partially purified flavanone synthase efficiently catalyzed the formation of malonyl pantetheine from malonyl-CoA and pantetheine. This malonyl transferase activity, and a general similarity with the condensation steps involved in the mechanisms of fatty acid and 6-methyl-salicylic acid synthesis from “acetate units”, are the basis for a hypothetical scheme which is proposed for the sequence of reactions catalyzed by the multifunctional flavanone synthase.

Genetics of alcohol dehydrogenase in Saccharomyces cerevisiae. II. Two loci controlling synthesis of the glucose-repressible ADH II.

Abstract: Two unlinked loci controlling the glucose-repressible alcohol dehydrogenase (ADH II) inSaccharomyces cerevisiae were investigated. One locus (AD R2) was characterized by electrophoreticallyslow andfast alleles and by inactiveadr2 mutant alleles. The ADH II pattern of heteroallelicslow × fast diploids indicates a tetrameric structure of the enzyme.AD R2 was considered as the structural gene, which codes for the ADH II subunits. Allelicadr2-f mutants could be classified by their response to theslow wild type allele (AD R2-S) in heter ozyg ous diploids. In most cases, only the slow band appeared. In threeadr2-f/AD R2-S crosses hybrid enzymes between inactive fast and active slow enzymes were formed. It was demonstrated, that allelic interactions at the protein level are not restricted to electrophoretical behaviour of hybrid enzymes. They also influence specific activities and substrate affinities.

Asymmetrical Distribution and Artifactual Reorientation of Lipopolysaccharide in the Outer Membrane Bilayer of Salmonella typhimurium

Abstract: Labelling of cell walls or outer membranes from Salmonella typhimurium with ferritin-conjugated antibodies directed against the polysaccharide moiety of the lipopolysaccharide gave the following results: 1. Cell walls or outer membranes from which the mucopeptide had been removed by lysozyme digestion at 0 degrees C carried the label on the outer face of the membrane. 2. When the murein layer was removed by either lysozyme or trypsin at physiological temperature (25-37 degrees C) subsequent labelling showed the lipopolysaccharide to be present on both membrane faces. 3. This reorientation could be achieved by a 1-min treatment of the membranes at 37 degrees C. 4. Glutaraldehyde fixation of the outer membranes did not entirely prevent but somewhat inhibited the temperature-induced reorientation process. 5. The same reorientation phenomenon was observed in lysozyme spheroplasts, which were prepared at 37 degrees C and were subsequently lysed in hypotonic medium at 0 degrees C. These observations are discussed as evidence for a transmembrane movement of lipopolysaccharide, which only takes place in areas where the mucopeptide layer is defective, and only when the temperature is sufficiently high to allow such movement.

Purification and properties of isoenzymes of cinnamyl-alcohol dehydrogenase from soybean-cell-suspension cultures.

Abstract: Two isoenzymes of an NADP+ -dependent cinnamyl alcohol dehydrogenase and an NAD+ - dependent aliphatic alcohol dehydrogenase were extracted from cell suspension cultures of soybean (Glycine max L., var. Mandarin) which form lignin during growth. These enzymes could be separated from each other by chromatography on DEAE-cellulose and hydroxyapatite. The cinnamyl alcohol dehydrogenase isoenzymes were partially purified by (NH4)2SO4 fractionation, and column chromatography on DEAE-cellulose, Sephadex G-100, and hydroxyapatite. The molecular weight of the enzymes were estimated by the elution volumes from a Sephadex G-100 column and were found to be about 43,000 (isoenzyme 1) and 69,000 (isoenzyme 2). Maximum rates of reaction were observed in the case of coniferyl alcohol oxidation at pH 9.2 (Isoenzyme 1) and pH 8.8 (isoenzyme 2); in the reverse reaction pH 6.5 was optimal for isoenzyme 2. Whereas isoenzyme 1 is specific for coniferyl alcohol, isoenzyme 2 can also oxidize cinnamyl alcohol and a number of substituted cinnamyl alcohols, Km values for substituted cinnamaldehydes are 3-11 times lower than for the corresponding alcohols. Neither isoenzyme reacted with benzyl alcohol, anisic alcohol or ethanol. Substrate inhibition for the forward and reverse reaction was found with isoenzyme 2 but not with isoenzyme 1. The equilibrium constant was determined to be about 10(9) in favour of coniferaldehyde reduction. The possible role of the cinnamyl alcohol dehydrogenase in lignin biosynthesis is discussed.

Sulfur Atoms as Ligands in Metal Complexes

Abstract: The types of sulfur bonding—as sulfane or sulfide—encountered in the molecules of maingroup elements are almost unknown in the chemistry of metal complexes, where the sulfur atoms function instead as two-electron donors by bridging two metal atoms, as four-electron donors by bridging three or four metal atoms, or as six-electron donors by incorporation between four metal atoms. In such complexes, the metal-metal bond can be modified over a wide range by chemical or electrochemical variation of the number of electrons present. The readiness with which polynuclear complexes containing metals and sulfur undergo redox reactions is also utilized by Nature in the active sites of some redox proteins.

Escherichia coli mutants uvr D and uvr E deficient in gene conversion of lambda-heteroduplexes.

Abstract: Calcium-treated cells of E. coli K-12 C600 were transfected with λ-heteroduplex DNA carrying the marker cIts857 in one strand and wildtype in the other. In single burst analyses of the phage progeny, 72–79% of the bursts were “pure” bursts containing either exclusively wildtype phage or exclusively mutant phage, indicating that conversion of the cIts857/+ mismatch to a homoduplex structure prior to replication occurred with this frequency. The r-strand1 appears to be “preferred”, since pure bursts of progeny with the r-strand genotype were almost twice as frequent as those with the l-strand genotype. Examination of the conversion frequency of a number of rec and uvr E. coli mutants showed that the mutants uvr D and uvr E are deficient in mismatch repair. conversion is reduced in the former by a factor of 2 and in the latter by a factor of 3.

The internal-alkaline pH gradient, sensitive to uncoupler and ATPase inhibitor, in growing Clostridium pasteurianum.

Abstract: 1 The intracellular pH was measured in growing Clostridium pasteurianum with and acid-base equilibrium distribution method [14C]Dimethyloxazolidinedione, [14]methylamine and [14C]acetic acid were used as "deltapH-indicators" During growth the extracellular pH decreased from 71 to 51; simultaneously the intracellular pH changed from 75 to 59 Thus, the intracellular pH was more alkaline than the extracellular pH by 04 to 08 pH-units 2 This pH gradient (interior alkaline) was abolished by the proton conductor carbonylcyanide m-chlorophenylhydrazone and the ATPase inhibitor N,N'-dicyclohexylcarbodiimide The pH gradient could not be demonstrated in cells depleted of an energy substrate These results suggest that the pH gradient is formed by an ATPase-driven extrusion of protons from the cells rather than by a Donnan potential 3 Growth of the organism was inhibited by low concentrations of both carbonylcyanide m-chlorophenylhydrazone (5 muM) and dicyclohexylcarbodiimide (5 muM) This finding suggests that the pH gradient is essential for the growing cell as it may be required for substrate accumulation and other types of transport processes

Nucleotide Pyrophosphatase of Rat Liver

Abstract: Studies on the subcellular distribution of ratliver nucleotide pyrophosphatase activity revealed its presence in the plasma membrane and the endoplasmic reticulum only The enzymes from either source were solubilized specifically with trypsin without an apparent change of their catalytic properties A 2000-fold and 1600-fold purification, respectively, was achieved by a procedure including DEAE-cellulose and affinity-chromatography with AMP as ligand, gel filtration on Sephadex G-200 and gel electrophoresis Both nucleotide pyrophosphatases were isolated as electrophoretically homogeneous soluble proteins They were shown to contain carbohydrate moieties The electrophoretic mobility of both enzymes in polyacrylamide gels was identical at three pH values Dodecylsulfate gel electrophoresis indicated a molecular weight of 137000 for both glycoproteins The enzymes hydrolyze a variety of purine and pyrimidine nucleotides yielding a 5′-nucleoside monophosphate Adenosine 3′:5′-monophosphate, nucleic acids and phosphate monoesters are not cleaved, but p-nitrophenyl-thymidine 5′-monophosphate is readily hydrolyzed In view of their substrate and inhibitor specificities the enzymes are considered nucleotide pyrophosphatases rather than phosphodiesterases

Social Learning of Vocal Patterns and Modes of their Application in Grey Parrots (Psittacus erithacus)1,2,3

Abstract: We have developed a method which allowed us to teach Grey Parrots special vocal patterns with a good success. The birds uttered these in antiphonal duets (Fig. 1, Table 1). The duets were performed only between the parrot and its cooperative partner. By experimental auditory stimulation we investigated the conditions of the vocal communication (Fig. 2, Fig. 3). Furthermore we found, that the performance of antiphonal duets obstructed the extension of the vocal repertoire with patterns which could not be learned from the birds' social partners (Fig. 4).

DNA replication patterns of human chromosomes from fibroblasts and amniotic fluid cells revealed by a Giemsa staining technique.

Abstract: A technique is described for visualizing late-replicating regions by a Hoechst 33258-Giemsa-staining procedure combining the techniques of Latt (1973) and of Perry and Wolff (1974). The advantages are

Photocontrol of phytochrome destruction in grass seedlings. the influence of wavelength and irradiance

Abstract: — –The kinetics of phytochrome destruction in vivo of coleoptiles and mesocotyls of etiolated grass seedlings (Avena sativa L., Zea mays L.) in continuous light were investigated using wavelength and irradiance as experimental variables. In contrast to dicotyledonous seedlings, the destruction reaction of these monocotyledons is saturated at very low levels of the far-red absorbing form of phytochrome, Pfr (e.g. at 1% of total phytochrome, corresponding to the photostationary state established by 727 nm light, in 2.5-day-old dark-grown Avena). On the other hand, the first-order rate constant of monocotyledon destruction may be at least one order of magnitude larger than in dicots, as indicated by the zero-order rate measured in the presence of saturating amounts of Pfr (τl/2 1.5 min in Avena). At sub-saturation Pfr levels, the destruction rate was found to be determined by the rate constants of the photoreactions over a wide range of wavelengths and irradiances. These results can be interpreted in terms of a destruction enzyme with high catalytic efficiency but limited availability. Analysis of in vivo binding of phytochrome to a pelletable cell structure during destruction revealed that both the pelletable and the non-pelletable fraction lose photoreversiblility with similar rates and thus provide no useful information with respect to a causal relationship between the two processes. However, due to the short half-life of Pfr at sub-saturation levels (which make the photoreactions and intermediary processes rate-limiting for destruction even at relatively high irradiances) the existence of a similarly rapid dark-reaction between the photoreactions producing Pfr and the destruction reaction could be demonstrated. This dark reaction displays the properties of Pfr binding to a receptor site.

Verhaltensgenetische Untersuchungen am akustischen Kommunikationssystem der Feldheuschrecken (Orthoptera, Acrididae)

Abstract: Bei den nah verwandten Feldheuschrecken derChorthippus-biguttulus-Gruppe stellt der fur jede Art charakteristische Gesang die wesentliche artisolierende Barriere dar, die unter naturlichen Bedingungen eine Bastardierung verhindert. BeiCh. biguttulus undmollis lies sich dieser akustische Isolationsmechanismus experimentell auser Kraft setzen, so das Kreuzpaarungen zustande kamen. Die Bastarde waren in ihrer Vitalitat nicht merklich eingeschrankt. 1. Im Gesang der Bastarde waren manche Musterelemente intermediar ausgebildet, wahrend andere sich uberlagerten. Daher wies der Bastard-Gesang einen hoheren Komplexitatsgrad auf als der Gesang beider Elternarten. Ein Teil der elterlichen Musterelemente wurde im Bastardgesang abgewandelt. So besas der Gesang der Bastard-Mannchen eine zeitliche Dynamik der Silben- und Schwirrlaut-Dauern, die bei den Elternarten fehlt. Die Uberlagerung desbiguttulus-eigeneu Silben-Musters und desmollis-eigenen Schwirrlaut-Musters macht wahrscheinlich, das diese Musterelemente der beiden Elternarten einander nicht homolog sind. 2. Die interindividuelle Variabilitat der Bastardgesange war verglichen mit der sehr geringen Variationsbreite der elterlichen Gesangsmuster erheblich vergrosert. Auch die individuelle Variation war bei vielen Bastarden groser als bei den Eltern. Das Durchsetzungsvermogen mancher elterlicher Musterelemente konnte sich von Gesang zu Gesang, oft auch innerhalb eines Gesanges, verandern. Bei manchen Bastard-♂ traten Storungen in der Bewegungskoordination der Singbeine auf. Solche Besonderheiten der Gesangsmuster waren oft fur ein Tier zeit seines Lebens charakteristisch. 3. Einige Beobachtungen liesen auf eine Korrelation zwischen artspezifischer Motivation und artspezifischen Gesangsmustern schliesen: Die Mannchen der einen Elternart (mollis) zeichnen sich durch eine langere und intensivere Werbung in der Balz aus. Manche Bastard-♂ sangen im Werbegesangmollis-ahnlicher, im Spontangesang aberbiguttulus-ahnicher. 4. Im Gesang der Bastard-Weibchen findet man im Prinzip dieselbe Uberlagerung der elterlichen Musterebenen wie im ♂-Gesang. 5. Der Gesang der Bastarde —sowohl derjenige der Mannchen, als auch der der Weibchen —war vom Kreuzungstyp abhangig: Im Mittel ahnelten die Gesange in allen untersuchten Parametern mehr dem Gesang der Mutterart. Wahrend bei den Mannchen geschlechtsgebundene Vererbung eine Rolle spielen konnte, mussen bei den (hinsichtlich ihres Chromosomensatzes reziprok gleichen) Bastard-Weibchen matrokline Effekte zugrundeliegen. 6. Einige der Beobachtungen weisen darauf hin, das sich im ZNS der Bastarde —entsprechend der artspezifischen Information jedes der beiden elterlichen Genomteile —streckenweise unabhangige Teilsysteme ausbilden konnten, deren konkurrierende Ausgange in einer gemeinsamen Endstrecke, vielleicht erst den Motoneuronen, konvergieren.

Intracellular proteinases in microorganisms.

Abstract: Publisher Summary One of the main functions of intracellular proteinases lies in their participation in protein turnover by the hydrolytic degradation of proteins. The rates of synthesis and degradation differ for the various enzymes and groups of enzymes. Moreover, they are influenced by many variables, such as nutritional conditions, growth phase, processes of differentiation. Protein synthesis is regulated at the level of transcription and translation by positive and negative control. The degradation of proteins is generally assumed to occur through the combined action of proteinases and peptidases, yielding amino acids after complete hydrolysis. On the other hand, it is possible that “limited proteolysis” leads to an accumulation of distinct macromolecular products that are either inactive or different in their catalytic properties from their uncleaved precursors. Microbial proteinases are commonly divided into intracellular and extracellular enzymes. Extracellular enzymes usually occur in the active state in the growth medium and are quite stable. Many of them are even available in large quantities allowing their application to medicine and industry.

Velocity dependence of total Penning ionization cross sections

Abstract: The velocity dependence of the total Penning ionization cross sections,σ(v), is measured in the thermal relative velocity region, using a time of flight method.σ(v) curves are reported for the collision systems He(21 S)/Ar, Kr, Xe, N2, Hg, He(23 S)/Ar, Kr, Xe, N2, Hg, Ne(3 P 2, 0)/Kr, Hg, and Ar(3 P 2, 0)/Hg. In a qualitative discussion it is shown that all features of the measuredσ(v) curves may be explained within the frame of the theory of Penning ionization, allowing to extract information on the physical quantities governing the process: on the interaction potentialV(R) and on the transition probabilityW(R). A theoretical calculation for the He(23 S)/Ar system shows good agreement with our experimentalσ(v) curve. On the basis of the present results earlier data onσ(v), and on absolute cross sections and rate constants obtained at certain relative velocity distributions are discussed.

Schwefelatome als Liganden in Metall‐Komplexen

Abstract: Die aus der Hauptgruppen-Molekulchemie gelaufigen Bindungsarten des Schwefels als Sulfan oder Sulfid sind in der Metallkomplex-Chemie fast unbekannt. Vielmehr fungieren hier Schwefelatome als Zweielektronen-Donor durch Verbruckung von zwei Metallatomen, als Vierelektronen-Donor durch Verbruckung von drei oder vier Metallatomen und als Sechselektronen-Donor durch Einbau zwischen vier Metallatomen. Durch chemische oder elektrochemische Variation der Elektronenzahl in den Komplexen last sich dabei die Metall-Metall-Bindung in weitem Bereich beeinflussen. Die Bereitschaft von Metall-Schwefel-Mehrkernkomplexen zu Redox-Reaktionen wird auch von der Natur in den aktiven Zentren einiger Redox-Proteine genutzt.

Photopic spectral sensitivity of the peripheral retina.

Abstract: Photopic spectral sensitivity was determined in the mid- and far-peripheral retina by two methods. The first consisted of measuring increment thresholds on a background similar in spectral composition to CIE Source A. The resulting spectral-sensitivity functions displayed maxima at about 440 nm, in agreement with previous work. The second method consisted of measuring dark-adaptation curves following termination of the background. From these curves, spectral-sensitivity functions were derived for various times in the dark. The results showed that the 440 nm maximum quickly diminished. When photopic thresholds were estimated from the cone plateau of the dark-adaptation curves, the spectral-sensitivity functions peaked at about 550 nm and had much the same shape from the parafovea to the far periphery. We suggest that previous findings of maximum photopic sensitivity in the short-wave region of the spectrum resulted from chromatic adaptation induced by backgrounds (such as Source A) that were weighted towards middle and long waves.

Kinetics of inactivation and recovery of the slow inward current in the mammalian ventricular myocardium.

Abstract: In order to study the kinetics of inactivation and recovery of the slow inward current in the mammalian ventricular myocardium voltage clamp experiments using the double sucrose gap technique were performed on isolated trabeculae and papillary muscles of cats. The separation of the slow inward current from the fast Na current was achieved by use of the conditioning clamp procedure. 1. The decay of the Ca current reflects the inactivation which develops due to depolarization. The rate of inactivation depends upon the membrane potential. Excess Ca (8.8 mM) accelerates the inactivation speed indicating that Ca ions not only act as charge carrier of the slow inward current but might influence in addition the kinetics of the slow membrane channel. In the presence of a lowered temperature a deceleration of inactivation (Q10 2.3) occurs. 2 If the membrane is repolarized a recovery process takes place restoring the availability of the slow membrane channel. As the inactivation the recovery rate depends upon the membrane potential. Excess Ca causes an acceleration whereas a decrease in temperature diminishes the recovery speed (Q10 2.3). Consequently, the Ca supply to the myocardial cell can be modified not only by changes of the transmembrane Ca concentration gradient or by an alteration of the Ca conductance of the slow channel but also by changes in the degree of recovery after a preceding Ca current. 3. Compared with the inactivation the recovery proceeds very slowly. Assuming that this slow recovery represents an inherent kinetic feature of the slow channel the kinetics of inactivation and removal of inactivation are not describable by a single inactivation variable (called as f by Reuter, 1973) which is of the Hodgkin-Huxley type. If a second inactivation variable (called as l) would be introduced additionally a formulation of the inactivation-recovery process of the slow membrane channel on the basis of the Hodgkin-Huxley model becomes feasible.

Prostaglandin, slow-reacting substance, and histamine release from anaphylactic guinea-pig hearts, and its pharmacological modification.

Abstract: Prostaglandins (Pgs), slow-reacting substance of anaphylaxis (SRS-A), and histamine were released from anaphylactic isolated perfused guinea pig hearts. Pgs were to the greatest part of the F2α-type. PgE2 was found in traces only. Neither PgA2, nor the metabolites 13,14-dihydro-15-keto-PgF2α and 13,14-dihydro-15-keto-PgE2 were detected in the perfusates. Isoproterenol reduced the PgF2α output significantly. This effect was increased by the addition of theophylline. Propranolol did not reverse the effect of isoproterenol, but in a high concentration (5 μg/ml) reduced the PgF2α output for its own. Indomethacin completely abolished the anaphylactic prostaglandin release.

Dynamics of liver glycogen: the topochemistry of glycogen synthesis, glycogen content and glycogenolysis under the experimental conditions of glycogen accumulation and depletion.

Abstract: Using histochemical techniques the glycogen content and the activities of glycogen synthetase (UDPGGT) and phosphorylase were studied in the livers of 106 golden hamsters under following experimental conditions: a) starvation of 16, 36, 48, 72 and 96 hours; b) alloxan-diabetes of 24, 48 and 72 hours; c) insulin-treatment (2 units, 30 min) after 24, 48 and 72 hours of alloxan diabetes. — Starvation leads to a depletion of liver glycogen during the first 48 hours, which is finally restricted to zone 3 of the liver acinus. After starvation of 72 and 96 hours a new glycogen accumulation is demonstrable in the microvasculatory periphery of the acinus (zone 3 and 2). The process of glycogen depletion is characterized in the beginning by a high phosphorylase activity in all zones of the acinus, later only in the forefield of glycogen content. The weak activity of glycogen synthetase is mainly restricted to zone 3. — All phases of glycogen depletion are to be found in alloxan diabetic animals, too. Out of 45 hamsters 23 showed an extreme depletion of glycogen; typical for this situation is a weak or absent glycogen synthetase activity in zone 3 and a broad field of phosphorylase activity in zones 1 and 2. The short stimulation by insulin leads to a considerable increase of glycogen synthetase activity at the portally oriented border of the glycogen area and to a shift of the moderate phosphorylase activity to zone 1.

Ammonium uptake by nitrogen fixing bacteria I. Azotobacter vinelandii.

Abstract: Both the changes in the activities of nitrogenase, glutamine synthetase and glutamate dehydrogenase and in the extracellular and intracellular NH4+ concentrations were investigated during the transition from an NH4+ free medium to one containing NH4+ ions for a continuous culture of Azotobacter vinelandii. If added in amounts causing 80–100% repression of nitrogenase, ammonium acetate, lactate and phosphate are absorbed completely, whereas chloride, sulfate and citrate are only taken up to about 80%. After about 1–2 hrs the NH4+ remaining in the medium is absorbed too, indicating the induction or activation of a new NH4+ transport system. One of the new permeases allows the uptake of citrate in the presence of sucrose. Addition of inorganic NH4+ salts leads to acidification of the culture. Anaerobiosis suppresses NH4+ transport.