Showing papers by "University of Konstanz published in 1973"

Effects of long-term electrical stimulation on some contractile and metabolic characteristics of fast rabbit muscles.

Abstract: Intermittant long-term stimulation of fast rabbit muscles up to 28 days with a frequency pattern resembling that of a slow muscle (10 Imp/sec) led to a slowing of the time course of contraction already during the first week. There was an increase of tetanic tension as well. The observed rearrangement of activities of key enzymes of energy supplying metabolism was found to occur sequentially. Decreases of extramitochondrial enzymes of glycogenolysis (phosphorylase), glycolysis (triosephosphate dehydrogenase, lactate dehydrogenase) and energy rich phosphate transfer were found initially together with a decrease of mitochondrial glycerolphosphate dehydrogenase. The isozyme pattern of lactate dehydrogenase was changed. Large initial increases were found in enzymes involved in glucose phosphorylation (hexokinase) and fatty acid activation (palmitoyl-CoA synthetase). Later an increase of key enzymes of the citric acid cycle (citrate synthase) and fatty acid oxidation (3-hydroxyacyl-CoA dehydrogenase) as well as ketone body utilization (3-ketoacid-CoA transferase) could be shown. Histochemical staining and comparative activity determination of succinate dehydrogenase in single fibres revealed that the mosaic like fibre composition of the fast muscle was transformed into a more uniform population resembling that of a predominantly slow muscle.

Channel formation kinetics of gramicidin A in lipid bilayer membranes.

Abstract: Previous studies have given evidence that the active form of gramicidin A in lipid bilayer membranes is a dimer which acts as an ion channel; it has been further shown that the mean lifetime of the channel strongly depends on the membrane thickness. As the thickness slightly decreases when a voltage is applied to the membrane, the equilibrium between conducting dimers and nonconducting monomers may be displaced by a voltage jump. From the relaxation of the electrical current after the voltage jump, information about the kinetics of channel formation is obtained. For a dioleoyllecithin/n-decane membrane the rate constant of association is found to be 2×1014 cm2 mole−1 sec−1, which is by three orders of magnitude below the limiting value of a diffusion-controlled reaction in a two-dimensional system. The dissociation rate constant is equal to 2 sec−1, a value which is consistent with the channel lifetime as obtained from electrical fluctuation measurements.

Valinomycin-mediated ion transport through neutral lipid membranes: influence of hydrocarbon chain length and temperature.

Abstract: Stationary electrical conductance experiments together with nonstationary relaxation experiments allow a quantitative determination of rate constants describing carrier-mediated ion transport Valinomycin-induced ion transport across neutral lipid membranes was studied The dependence of the transport parameters on the chain length of the lipid molecules, on the kind of alkali ion, and on the temperature was determined The relaxation time τ the current following a voltage jump shows a marked increase with decreasing temperature or with increasing chain length of the lipid molecules This variation of τ is interpreted on the basis of a varying membrane fluidity It is shown that under favorable circumstances the equilibrium constant of complex formation in the aqueous phase may be obtained from membrane experiments Furthermore, the kinetics of exchange of valinomycin between membrane and water was studied We found a marked influence of the totus surrounding the black film on the kinetics as well as on the total amount of valinomycin molecules in the membrane The problem of location of the free carrier molecules inside the membrane is discussed

Planung als politischer Prozess

Abstract: Das Interesse fur die ≫Politik der Planung≪scheint in besonderem Mase abhangig von dem jeweils vorausgesetzten Politikbegriff: Wo Politik als Aufgabenerfullung, als ≫Zukunftsbewaltigung≪1, als ≫policy≪begriffen wird, da wird man auch leicht zu dem Schlus kommen, ≫das Planung als Gesamtprozes tatsachlich nichts anderes ist als ein Beitrag zur Rationalisierung der Politik≪2. Wo man jedoch Politik vor allem als konflikthaften Prozes, als Auseinandersetzung um Machtanteile, als ≫politics≪begreift, da wird man die Distanz zwischen ≫sachlicher≪Planung und unsachlicher Politik3 oder umgekehrt die Irrelevanz der ≫unpolitischen≪Planung fur den politischen Prozes der Konfliktaustragung und Konsensbildung hervorheben4. Zur Verdeutlichung der relativen Berechtigung wie der Grenzen beider Perspektiven bedarf es zunachst einer knappen Explikation des hier vorausgesetzten Begriffs der Politik. Ausgangsproblem der Politik ist die Moglichkeit kollektiven Handelns bei nicht vorauszusetzendem Konsens. Diese Moglichkeit ist nicht zugleich auf den Modus der Herstellung bindender Entscheidungen zu reduzieren5; gemeinsames Handeln kann durch unerzwungene Solidaritat, durch Bargaining, durch Einflus6, Macht oder Zwang von Fall zu Fall ermoglicht werden7 — so vor allem im Bereich der intersystemischen und internationalen Politik. Jedoch werden der Anwendungsbereich und die Wirksamkeit kollektiven Handelns durch die institutionalisierte Moglichkeit bindender Entscheidungen, fur die Gehorsam im allgemeinen erwartet werden kann, auserordentlich erweitert. Zugleich begrundet die Trennung von Entscheidung und Ausfuhrung auch die Differenzierung der Rollen der ≫Beteiligten≪und der ≫Betroffenen≪und damit das Herrschaftsproblem der Politik8.

NMR.‐Study of Nitrogen Inversion and Conformation of 1,5‐Dihydro‐isoalloxazines (‘Reduced Flavin’). Studies in the flavin series, XIX. Communication

Abstract: The pyramidal inversion of the N(5)-centre of several reduced flavins was measured by NMR. The inversion barrier was found to be ∼10 kcal/mol in acetone solutions and to be independent of the size of the N(5) substituent. An increase of the inversion barrier of ∼5 kcal/mol was observed in the case where the N(5) substituent could only be in axial position, and an increase of ∼3.5 kcal/mol was observed for an acyl-like N(5) substituent. In aqueous solution the inversion barrier increases by ∼3 kcal/mol. The stereochemistry of reduced flavin and its potential relevance in flavin-dependent biological dehydrogenations is discussed.

Specific characterization of isoelectrofocused immunoglobulins in polyacrylamide gel by reaction with 125 I-labeled protein antigens or antibodies.

Abstract: A method is described for the visualization and characterization of isoelectrofocused antibodies, immunoglobulins in general, and many other proteins in thin plates of polyacrylamide gel. The novel aspect of the method is that the protein bands after electrofocusing are immobilized in the gel by treatment with glutaraldehyde after soaking with 18 % sodium sulfate solution. Such treatment is shown not to affect the binding activity of antibodies. Antibody bands are located by treatment of the plates with 125I-labeled specific antigen. Other proteins can be located by 125I-labeled specific antibody. The bands thus located are visualized by radioautography. The immobilization of the focused proteins allows the excess radiolabeled reagent macromolecules to be washed out of the plates without disrupting the focused pattern. Under the conditions described, background radioactivity and nonspecific pickup by other serum proteins in the plates are negligible. Examples of the use of the method are given for anti-4-azonaphthalene-1-sulfonate and anti-4-hydroxy-5-iodo-3-nitro-phenacetyl antibodies, using the 125I-labeled hapten-specific antigens, and for a mouse IgG myeloma protein, MOPC 195, using 125I-labeled goat anti-mouse IgG antibody. Extension of the method would allow differences between proteins to be characterized by appropriate 125I-labeled antibodies. Thus immunoglobulins could be characterized by 125I-labeled antibodies specific for immunoglobulin markers (e.g. Ig class, L chain type, etc.). The advantages of this method over other methods include the ease and generality of using radioiodine labeled macromolecules – especially antibodies – as compared to the restriction imposed by other methods which require small labeled ligands. The method can be extended to the use of fluorescent-labeled proteins and radiolabeled polysaccharide antigens as locators.

Isometric training of rats — Effects upon fast and slow muscle and modification by an anabolic hormone (Nandrolone Decanoate)

Abstract: Some effects of isometric exercise were studied in fast rectus femoris muscle and slow soleus muscle of the female rat. Isometric twitch contraction time shortened by 20% in fast and prolonged by 20% in slow muscle. Maximum tetanic tension increased by 20% in the fast muscle. Changes in the enzyme activity pattern of energy supplying metabolism differed in the two muscles. The different responses may be explained by different topography and differences in fibre composition. There was an increase in creatine kinase, glycogen phosphorylase and triosephosphate dehydrogenase in rectus femoris muscle. The same enzymes were found to decrease slightly in soleus muscle. Treatment of the animals with Nandrolone Decanoate caused a higher performance of the trained animals. In the rectus femoris muscle hormone treatment alone caused similar increases in glycogenolytic and glycolytic enzymes as did training. Additionally, an increase of glycogen synthetase was induced by the hormone. These changes could not be increased by additional training. In soleus muscle hormone treatment alone caused a decrease in muscle strength. In hormone treated exercising animals the prolongation of isometric twitch contraction time was not found.

Effects of short-term, high intensity (sprint) training on some contractile and metabolic characteristics of fast and slow muscle of the rat.

Abstract: Effects of a three weeks lasting short-term, high intensity training (sprint training) upon contractile parameters and selected enzyme activities of energy-supplying metabolism in slow soleus and fast rectus femoris muscle were investigated in female rats Isometric twitch contraction time decreased in the soleus muscle Maximum tetanic tension was found increased in soleus and rectus femoris muscle Increases in hexokinase and citrate synthetase activities were induced in both muscles In soleus muscle there was also an increase of glycogen phosphorylase, triosephosphate dehydrogenase and creatine kinase activities Increases in the activity of the reference enzyme of fatty acid oxidation as known to be typical for endurance exercise, were neither found in rectus femoris nor in soleus muscle

Acetylcholine as sensory transmitter in crustacea

Abstract: 1. A method is described for the perfusion of the thoracic ganglia of crabs (Cancer, Pugettia, Portunus, Callinectes, Eriphia) through the sternal artery. 2. Administration of acetylcholine (ACh)via perfusion elicits leg movements. The effect is enhanced by the anticholinesterase eserine. Eserine alone causes great enhancement of reflex activity. 3. Eserinized perfusate collected during periods of sensory stimulation (optical or tactile stimuli) contained ACh as detected by bioassay on isolated mollusc ventricles. Up to 2 × 10−9 g of ACh were liberated per minute. No ACh was detectable in perfusates collected from quiescent, unstimulated crabs (detection limit 1−10 × 10−11g/ml) or from stimulated crabs when the perfusion fluid contained no eserine. Eserine itself had no effect on the heart preparations used. 4. The demonstration of a release of ACh from the central nervous system of crabs during sensory stimulation represents the last missing link in the evidence (which is fully reviewed) that ACh is the transmitter substance of sensory neurons in decapod crustacea and, presumably, in other arthropod groups as well.

Nucleoside, IX. Synthese und Eigenschaften von Lumazin-nucleosiden — Strukturanaloga des Uridins und Thymidins

Abstract: Die Umsetzungen von Lumazin (1), seinem, 6,7-Dimethyl- (2) und 6,7-Diphenyl-Derivat (3) mit I-Halogen- bzw. 1-Acyloxyribose- und 2-Desoxyribose-Derivaten nach der Silyl-Methode werden beschrieben. Als Hauptprodukte werden die Lumazin- N-1-nucleoside gebildet. l,3-Diglycoside entstehen in untergeordnetem Mase, wahrend die N-3-Nucleoside meist nur in Spuren nachweisbar sind. Die Strukturen der neu synthetisierten Produkte werden durch UV- und NMR-spektroskopische Untersuchungen gesichert. Nucleosides, IX. Synthesis and Properties of Lumazine Nucleosides — Structural Analogs of Uridine and Thymidine Glycosidation reactions of lumazine (1) and its 6,7-dimethyl (2) and 6,7-diphenyl derivative (3) with 1-halo- and 1-acyloxyribose and 2-deoxyribose derivatives respectively via the silyl method are described. The main reaction products turned out to be the lumazine-N-1 nucleosides. 1,3-Diglycosides are formed in minor amounts whereas in most cases the N-3 nucleosides are present only in trace quantities. The structures of the newly synthesized reaction products have been established by u. v. and n. m. r. spectra.

d-Galactose Dehydrogenase from Pseudomonas saccharophila

Abstract: 1 d-Galactose dehydrogenase from Pseudomonas saccharophila has been purified over 700-fold with an over-all yield of 27%. The purified enzyme exhibits a specific activity of about 200 μmol NADH formed × min−1× mg protein−1 and has been shown to be homogeneous by ultracentrifugation and by gel electrophoresis. 2 The amino acid composition of the enzyme has been determined. 3 The native enzyme has a sedimentation coefficient (S20,w0) of 5.94 S and a diffusion coefficient (D20,w0) of 5.60 F. The experimentally determined partial specific volume (v) is 0.744 ml/g. The molecular weight calculated from these data is 103000, in good agreement with the value of 102000 estimated by gel permeation chromatography. 4 The enzyme dissociates into polypeptide chains in the presence of 5 M guanidine hydrochloride or 0.1% sodium dodecylsulfate. The molecular weight of the polypeptide chains has been found to be 25000 by ultracentrifugation (S20,w0= 1.35 S, D20,w0= 5.28 F) and by dodecylsulfate-polycrylamide electrophoresis. The native enzyme is composed of four polypeptide chains. 5 The pI of d-galactose dehydrogenase is 5.1. The pH-optimum is between pH 8–9 in Tris-HCI buffer. AT PH 8.6 and 30°C the limiting michaelis constant for NAD+ is Ka= 0.14 mM, the limiting michaelis constant for d-galactose is Kb= 1.0 mM and the dissociation constant for NAD+ is Kia= 0.48 mM. 6 The enzyme is specific for NAD and uses NADP only to a minor extent as a coenzyme. It oxidizes the following sugars arranged according to relative rates, in decreasing order: d-FUCOSE > d-galactose > 3-deoxy-d-galactose > 2-deoxy-d-galactose > 4-deoxy-d-galactose > l-arabinose > 2-deoxy-2-amino-d-galactose.

Function and Purification of Gene 4 Protein of Phage T7

Abstract: T7 mutant in gene 4 synthesizes only short DNA fragments complementary to the H strand. By an in vitro complementation system which starts from intact T7 DNA, gene 4 protein has been purified.

Appendix: Structure and conformation of bilirubin. Opposing views that invoke tautomeric equilibria, hydrogen bonding and a betaine may be reconciled by a single resonance hybrid

Abstract: A novel conformational structure of bilirubin is presented which obtains maximum stabilization through a system of four intramolecular hydrogen bonds. Two hydrogen bonds link oxygen and nitrogen atoms of each end ring to the contralateral carboxyl group. The proposed structure can explain a variety of uncommon features of bilirubin, and reconciles many seemingly contradictory hypotheses by accommodating them in individual structures which are mesomeric forms of one resonance hybrid. In the light of this newly conceived structure the following characteristics of bilirubin are re-evaluated: the stability of the compound, its reaction with diazomethane, the conformational behaviour of its dimethyl ester, its spectral properties, the chirality of the compound when complexed to serum albumin, and the structure of its metal chelates.

Nucleoside, XIII. Synthese und Eigenschaften von Lumazin‐ und Isopterin‐glucosiden

Abstract: Die Glucosidierung von Lumazin (l), Isopterin (2) sowie seinem 6,7-Dimethyl-Derivat (3) nach der „Silyl-Methode” wird beschrieben. Als Hauptreaktionsprodukte entstehen die N-l-Substitutionsprodukte, die in Form ihrer Tetra-O-acetyl-Derivate (8, 10, 14) und der freien Glucoside 9 und 11 isoliert werden. Die Charakterisierung erfolgt durch UV- und NMR-spektroskopische Untersuchungen, wobei aus letzteren erstmals ein experimenteller Beweis uber das Vorliegen von rotationsgehinderten syn-anti-Isomeren erbracht werden kann. Die freien Aktivierungsenergien der Isomerisierung haben Werte um 18 kcal/mol. Nucleosides, XIII. Synthesis and Properties of Lumazine and Isopterin Glucosides The glucosidation of lumazine (l), isopterin (2) and its 6,7-dimethyl derivative (3) via the „silyl method” is described. The reaction favours N-1 substitution and the tetra-O-acetyl derivatives 8, 10 and 14 as well as the free glucosides 9 and 11 have been isolated and characterized by u.v.- and n.m.r. spectrophotometric studies. The latter provided for the first time an experimental proof for the existence of rotationally restricted syn-anti-isomers at room temperature. The free energies of activation of the isomerization have values around 18 kcal/mol.

Flavin-o2 interaction mechanisms and the function of flavin in hydroxylation reactions

Abstract: Molecular oxygen is a species with triplet ground state, which is of exceptional kinetic stability owing to the nearly spherical symmetry of its electron distribution. Life depends on the resulting chemical inertness of 02, as well as on the various modes of Oy activation provided by nature in order to maintain oxygen metabolism. Such an activation must induce an (electric) perturbation of orbital symmetry in the 02 molecule, andat the same time a magnetic perturbation, in order to overcome the forbiddenness of multiplicity changes. Hence the sequence of possible reactions in the O2 activation process consists of the formation of an oxygen adduct (Equation I ) , whose decay must compete effectively with its formation (or else the adduct will be an oxygen stabilizer, as with hemoglobin). The decay may occur in a radical mode, yielding superoxide (Equation 2), or (more frequently) in an ionic mode, yielding peroxide (Equation 3). The formation of superoxide from O2 is endothermic as such, and it implies the transfer of one electron only, while peroxide formation, which implies the transfer of two electrons, is energetically favored under most conditions.’ It is, therefore, a widespread mistake to assume that autoxidation reactions at low temperatures would mostly, or even just frequently, occur through radicals as primary intermediates. A third way of 0, adduct decay implies the formation of ternary complexes (Equation 4), which leads to oxygenation of the third species then called a substrate (Equation 5 ) . A + 02 F’ A-0, (A = activator) (1)

Temperature dependence of the electrical resistivity in amorphous metals

Abstract: In amorphous metals the electrical resistivity increases linearly in the temperature range from 2 to 40 K. This result differs fundamentally from the nonlinear behaviour known for crystalline metals and it suggests the conduction electrons not to be scattered by the vibrations of the amorphous point lattice. The temperature dependent part of the resistivity in amorphous metals is explained with scattering of conduction electrons by fluctuations ofp-electrons.

The relation between blood flow and enzymatic activities in slow and fast muscles during development.

Abstract: Blood flow and activity of oxidative and glycolytic enzymes was studied in slow- and fast-twitch muscles in kittens and in slow and fast muscles in chicks in the course of postnatal development. Soleus (in kittens) and anterior latissimus dorsi (in chicks) were used as representatives of slow muscles, gastrocnemius (in kittens) and posterior latissimus dorsi (in chicks) as representatives of fast-twitch muscles. Blood flow measured by133Xe clearance was similar in soleus and gastrocnemius (20 ml/100 g x min) during the first week of life. Later, blood flow increased slightly in soleus, and bccame considerably lower in gastrocnemius. The first significant difference was observed in 5-week-old kittens, where the blood flow was 2.4 times higher in soleus than in gastrocnemius. In adult cats blood flow (measured by photoelectric drop-counter) was 39.8±12.7 ml/100 g tissue x min in soleus, and 7.0±1.5 ml/100 g x min in gastrocnemius. The number of open capillaries per muscle fibre (studied in histological sections after India ink injection) was always higher in muscles with higher blood flow, and in 35-day-old kittens was significantly higher in soleus than in gastrocnemius. The activity of the two oxidative enzymes measured (citrate synthase and 3-hydroxyacetyl-CoA-dehydrogenase) was higher in soleus than in gastrocnemius in one-day-old kittens, and this proportion did not change substantially during further development. The activity of both enzymes increased in both muscles after 21 day of age. The activity of glycolytic enzymes (lactate dehydrogenase and triosephosphodehydrogenase) was similar in both muscles in kittens up to 21 days; thereafter, their activity increased much more rapidly in gastrocnemius than in soleus. In chickens, in which electromyographic activity, in both slow and fast muscles decreased during postnatal development, the activity of oxidative enzymes decreased as well, the decrease being greater after the 4th day in fast muscle in slow. Similarly, blood flow which was the same in both muscles until 8 days of age decreased more in the course of further development in fast than in slow muscles.

The effect of potassium diffusion through the Schwann cell layer on potassium conductance of the squid axon.

Abstract: The accumulation of K+ ions in the intermembranous spaces of the Schwann cell layer during K+ ion current flow may lead to appreciable changes of the K+ equilibrium potential. Thus, for an evaluation of the K+ conductance of the axolemma, the transport of K+ ions through the Schwann cell layer has to be characterized quantitatively. In the present work this is done for a simplified model of the geometrical arrangement of the slit-like channels traversing the Schwann cell region.