Showing papers by "University of Konstanz published in 1985"

Neural control of phenotypic expression in mammalian muscle fibers.

Abstract: In this review, the present knowledge about the mechanisms involved in the control of the phenotypic expression of mammalian muscle fibers is summarized. There is a discussion as to how the activity imposed on the muscle fibers by the motoneuron finally induces in the muscle cells the expression of those genes that define its particular phenotype. The functional and molecular heterogeneity of skeletal muscle is thus defined by the existence of motor units with varied function, while the homogeneity of muscle fibers belonging to the same motor unit is yet another indication of the importance of activity in the control of gene expression of the mammalian muscle fiber.

Ion selectivity of gram-negative bacterial porins.

Abstract: Twelve different porins from the gram-negative bacteria Escherichia coli, Salmonella typhimurium, Pseudomonas aeruginosa, and Yersinia pestis were reconstituted into lipid bilayer membranes. Most of the porins, except outer membrane protein P, formed large, water-filled, ion-permeable channels with a single-channel conductance between 1.5 and 6 nS in 1 M KCl. The ions used for probing the pore structure had the same relative mobilities while moving through the porin pore as they did while moving in free solution. Thus the single-channel conductances of the individual porins could be used to estimate the effective channel diameters of these porins, yielding values ranging from 1.0 to 2.0 nm. Zero-current potential measurements in the presence of salt gradients across lipid bilayer membranes containing individual porins gave results that were consistent with the conclusions drawn from the single-channel experiments. For all porins except protein P, the channels exhibited a greater cation selectivity for less mobile anions and a greater anion selectivity for less mobile cations, which again indicated that the ions were moving inside the pores in a fashion similar to their movement in the aqueous phase. Three porins, PhoE and NmpC of E. coli and protein P of P. aeruginosa, formed anion-selective pores. PhoE and NmpC were only weakly anion selective, and their selectivity was dependent on the mobility of the ions. In contrast, cations were unable to enter the selectivity filter of the protein P channel. This resulted in a high anion selectivity for all salts tested in this study. The other porins examined, including all of the known constitutive porins of the four gram-negative bacteria studied, were cation selective with a 3- to 40-fold preference for K+ ions over Cl- ions.

Porin from bacterial and mitochondrial outer membranes.

Abstract: The outer membrane of gram-negative bacteria acts as a molecular filter with defined exclusion limit for hydrophilic substances. The exclusion limit is dependent on the type of bacteria and has for enteric bacteria like Escherichia coli and Salmonella typhimurium a value between 600 and 800 Daltons, whereas molecules with molecular weights up to 6000 can penetrate the outer membrane of Pseudomonas aeruginosa. The molecular sieving properties result from the presence of a class of major proteins called porins which form trimers of identical subunits in the outer membrane. The porin trimers most likely contain only one large but well-defined pore with a diameter between 1.2 and 2 nm. Mitochondria are presumably descendents of gram-negative bacteria. The outer membrane of mitochondria contains in agreement with this hypothesis large pores which are permeable for hydrophilic substances with molecular weights up to 6000. The mitochondrial porins are processed by the cell and have molecular weights around 30,000 Daltons. There exists some evidence that the pore is controlled by electric fields and metabolic processes.

Biochemical and ultrastructural changes of skeletal muscle mitochondria after chronic electrical stimulation in rabbits.

Abstract: The purpose of the present investigation was to follow and correlate changes of structural and biochemical markers of energy metabolism during chronic electrical stimulation of tibialis anterior muscle in rabbits In the superficial portion of the muscle, 5 to 6-fold increases occurred in enzyme activities of the citric acid cycle and of fatty acid oxidation after 28 days of stimulation Enzyme activity changes in the deep, more oxidative part of the muscle were relatively smaller Consequently, levels of the citric acid cycle enzymes became similar in superficial and deep parts of the muscle after the longest stimulation periods With the exception of hexokinase, which increased in parallel with the citric acid cycle enzymes, glycolytic enzymes decreased 2 to 3-fold Muscle mass and fibre size remained unchanged, while capillary density and capillary to fiber ratio increased 2-fold The volume density of total mitochondria increased in a fashion similar to the changes of the enzymes of the citric acid cycle (7-fold in superficial and 35-fold in deep parts of the muscle) and, thus, approached values found in heart muscle Disproportionate changes in enzyme activities of ketone body utilisation and of mitochondrial glycerolphosphate oxidase indicated qualitative changes within the mitochondrial population However, the proportion of subsarcolemmal to interfibrillar mitochondria, as well as the area of inner mitochondrial membrane per unit volume of mitochondrion remained unchanged Similarly, intracellular lipid deposits remained unchanged with stimulation It is concluded that there is an excellent agreement between morphometric and biochemical measurements of tissue oxidative capacity

Survival of sulfate-reducing bacteria after oxygen stress, and growth in sulfate-free oxygen-sulfide gradients

Abstract: Summary The survival after oxygen stress was studied with eight species of sulfate-reducing bacteria. In the absence of sulfide all species tolerated 6 min of aeration without loss of viability. Even after 3 h of aeration the viability of four species ( Desulfovibrio vulgaris, D. desulfuricans, D. salexigens and Desulfobacter postgatei ) was not impaired. Four other species were sensitive to 3 h of aeration: the surviving fractions of Desulfotomaculum ruminis, D. nigrificans and Desulfococcus multivorans were about 1%, that of Desulfotomaculum orientis about 0.01%. Formation of spores resulted in oxygen resistance of D. orientis . Reducing agents did not protect the vegetative cells of this strain against oxygen toxicity. In contrast, sulfhydryl group-containing agents increased the oxygen sensitivity considerably. Growth of sulfate- and sulfur-reducing bacteria in oxygen-sulfide gradients in agar tubes was studied. In the gradients these strictly anaerobic bacteria revealed oxygen-dependent growth in sulfate- and sulfur-free medium. Three sulfate-reducing bacteria that could not use thiosulfate or sulfur as electron acceptor failed to grow in oxygen-sulfide gradients. Obviously, not directly molecular oxygen, but oxidation products of sulfide, such as thiosulfate or sulfur, were used as electron acceptors and were continuously regenerated in a cycling process from sulfide by autoxidation. The conceivable ecological significance of a short sulfur cycle driven by autoxidation of sulfide is discussed.

Nitrous oxide reductase from denitrifying Pseudomonas perfectomarina. Purification and properties of a novel multicopper enzyme.

Abstract: Nitrous oxide reductase from the denitrifying bacterium Pseudomonas perfectomarina has been isolated and purified to homogeneity The enzyme contained about eight copper atoms/120 kDa and was composed of two presumably identical subunits The isoelectric point was 51 Several spectroscopically distinct forms of the enzyme were identified A 'pink' form of the enzyme was obtained when the purification was done aerobically The specific activity of this species was around 30 nkat/mg protein as measured by the nitrous-oxide-dependent oxidation of photochemically reduced benzyl viologen A 'purple' form of the enzyme, whose catalytic activity was 2-5-fold higher, was obtained when the purification was done anaerobically The activity of both forms of the enzyme was substantially increased by dialyzing the protein against 2-(N-cyclohexylamino)ethanesulfonate buffer at pH approximately equal to 10 A maximal activity of 1000 nkat/mg protein has been obtained for the purple form using this procedure A 'blue', enzymatically inactive form of the enzyme resulted when either the pink or the purple species was exposed to excess dithionite or ascorbate Anaerobic, potentiometric titrations of both the purple and the pink form of the enzyme gave a Nernst factor, n540, of 095 and a midpoint potential, E'0,540 of +260 mV (vs SHE, 25 degrees C, Tris/HCl buffer, pH 75) Electron paramagnetic resonance (EPR) and optical spectra of N2O reductase suggested the presence of an unusual type 1 copper center Type 2 copper was absent The hyperfine splitting in the g parallel region consisted of a seven-line pattern In the presence of excess of reductant, a broad EPR signal with g values at 218 and 206 was observed The EPR spectra of the pink and purple forms of the enzyme were similar; however, the spectrum of the purple form was better resolved with g parallel = 218 (A parallel = 383 mT) and g perpendicular = 203 (A perpendicular = 28 mT) Most of the copper in N2O reductase was removed by anaerobic dialysis against KCN Reaction of the apoprotein with Cu(en)2SO4 partially regenerated the optical and EPR spectra of the holoprotein; the resulting protein was enzymatically inactive Monospecific antibodies against the copper protein strongly inhibited the N2O reductase activity of purified samples and cell-free extracts

Growth with hydrogen, and further physiological characteristics of Desulfotomaculum species

Abstract: Growth of Desulfotomaculum orientis, D. ruminis, D. nigrificans and the Desulfotomaculum strains TEP, TWC and TWP, that were newly isolated with sulfate and fatty acids, was studied using defined mineral media. Four of these strains grew with hydrogen plus sulfate as the only energy source. Under these conditions the growth yield of D. orientis in batch culture was 7.5 g cell dry mass per mol sulfate reduced. Growth on methanol with growth yields of about 6 g cell dry mass per mol sulfate was obtained with D. orientis and strain TEP. All strains tested grew slowly with formate as electron donor. Fatty acids from propionate to palmitate were utilized by the strains TEP, TWC and TWP. D. orientis and the strains TEP and TWC were able to utilize the methoxyl groups of trimethoxybenzoate for growth. D. orientis was found to grow chemoautotrophically with hydrogen, carbon dioxide and sulfate; during growth with C1-compounds no additional organic carbon source was required. Furthermore, D. orientis was able to grow slowly in sulfate-free medium with formate, methanol, ethanol lactate, pyruvate or trimethoxybenzoate. Under these conditions acetate was excreted, indicating the function of carbon dioxide as electron acceptor in a homoacetogenic process. A growth-promoting effect of pyrophosphate added to the medium of Desulfotomaculum species was not observed. The results show a high catabolic and anabolic versatility among Desulfotomaculum species, and indicate that electron transport to sulfate can be the sole energy conserving process in this genus.

Fermentation of acetylene by an obligate anaerobe,Pelobacter acetylenicus sp. nov.

Abstract: Four strains of strictly anaerobic Gram-negative rod-shaped non-sporeforming bacteria were enriched and isolated from marine and freshwater sediments with acetylene (ethine) as sole source of carbon and energy. Acetylene, acetoin, ethanolamine, choline, 1,2-propanediol, and glycerol were the only substrates utilized for growth, the latter two only in the presence of small amounts of acetate. Substrates were fermented by disproportionation to acetate and ethanol or the respective higher acids and alcohols. No cytochromes were detectable; the guanine plus cytosine content of the DNA was 57.1±0.2 mol%. Alcohol dehydrogenase, aldehyde dehydrogenase, phosphate acetyltransferase, and acetate kinase were found in high activities in cell-free extracts of acetylene-grown cells indicating that acetylene was metabolized via hydration to acetaldehyde. Ethanol was oxidized to acetate in syntrophic coculture with hydrogen-scavenging anaerobes. The new isolates are described as a new species in the genusPelobacter, P. acetylenicus.

Inferior colliculus of the house mouse. I. A quantitative study of tonotopic organization, frequency representation, and tone-threshold distribution

Abstract: Electrophysiological mapping was used to study frequency representation in the inferior colliculus (IC) of the mouse. In the lateral nucleus (LN) only part of the frequency range of hearing was represented and tonotopicity was separate from that in the rest of the IC. Highest frequencies occupied the medial part (M) of the central nucleus (CN). A single complete representation of the hearing range was present only if representations in the dorsal cortex (plus dorsomedial nucleus) and CN (including M) were combined. Continuous isofrequency planes making up these nuclei (without the lateral part of the CN) were reconstructed. They tilted from medial to lateral and from caudal to rostral. The steepness of the slopes increased from caudal to rostral and from dorsal to ventral (i.e., with increasing frequency). Isofrequency planes had similar angles of deviation from the horizontal plane as described for dendritic laminae in the CN. Differences of mapping in the lateral part of the CN from that in the rest of the CN could be explained by the different organization of laminae in this part. The relative amounts of IC depth and volume occupied by parts of the mouse audible frequency range were quantified. Frequency representation along IC depth was not proportional to that along cochlear length. Compared with the relative density of afferent nerve fiber supply within given frequency ranges represented along the basilar membrane, there is a relative under-representation in the IC up to 15-20 kHz and an over-representation of higher frequencies. Highest absolute tone sensitivity (lowest threshold) was found in neurons forming a column (running perpendicular to isofrequency planes) in the center of the IC. Results are discussed with regard to frequency representation, intrinsic neuronal organization, and functional segregation in the IC of mammals.

Cortical and subcortical afferent connections of the primate's temporal pole: a study of rhesus monkeys, squirrel monkeys, and marmosets

Abstract: The afferent connections of the primate's temporopolar cortex were investigated with the retrograde horseradish peroxidase technique. Old World and New World monkeys received small unilateral injections of horseradish peroxidase. These labeled cells in a number of cortical, thalamic, and brainstem regions and in a few further telencephalic and diencephalic regions. Cortically, the neighboring areas of the inferior and superior temporal gyrus and the insula contained a considerable number of labeled cells. Furthermore, a substantial projection arose from the orbitofrontal and the frontopolar cortex. The cingulate gyrus contained only very few labeled cells. Interhemispherically, corticocortical connections arose mainly from temporal lobe areas. Labeled cells were seen in various regions of the basal forebrain and cells labeled only faintly in the lateral and basal accessory nuclei of the amygdala. The claustrum contained labeled neurons only in one rhesus monkey. On the diencephalic level, the caudal medial portion of the medial pulvinar was the principal thalamic source of afferents to the temporopolar cortex. Furthermore, labeled cells were found in the neighboring, caudal part of the mediodorsal nucleus, within and along the nucleus limitans, in the medial geniculate nucleus, and in several nuclei of the nonspecific system. The fields of Forel, the zona incerta, and lateral and dorsomedial hypothalamic areas contained a few labeled cells. Within the brainstem of the rhesus monkeys those regions projecting diffusely to the cortex contained a few labeled neurons. Furthermore, these brains had some labeled cells in the regions of the nuclei medialis annuli aqueductus, tractus mesencephalicus nervi trigemini, and trochlearis. Although among the three species differences in the cortical and thalamic projection patterns were observed, the regions projecting most densely to the temporal pole were similar in principle. This statement holds in particular for cortical and thalamic sites. However, the greatest number of labeled cells was found in the rhesus monkey, a fact that cannot be attributed solely to the size of the horseradish peroxidase injections and the size of the brain, but that appears rather to represent a true species difference. From our results we conclude that the temporopolar cortex constitutes a cortical area necessary for effective affectional-sensory integration.

Anaerobic oxidation of fatty acids by Clostridium bryantii sp. nov., a sporeforming, obligately syntrophic bacterium

Abstract: From marine and freshwater mud samples strictly anaerobic, Gram-positive, sporeforming bacteria were isolated which oxidized fatty acids in obligately syntrophic association with H2-utilizing bacteria. Even-numbered fatty acids with up to 10 carbon atoms were degraded to acetate and H2, odd-numbered fatty acids with up to 11 carbon atoms including 2-methylbutyrate were degraded to acetate, propionate and H2. Neither fumarate, sulfate, thiosulfate, sullur, nor nitrate were reduced. A marine isolate, strain CuCal, is described as type strain of a new species, Clostridium bryantii sp. nov.

Dispersed ionic conductors and percolation theory.

Abstract: We suggest that ionic conductors containing a dispersed insulating phase are suitable materials for investigating static and kinetic aspects of percolation. We develop a lattice model for the two-phase mixture with special emphasis on the role of an enhanced interface conductivity. By using two-dimensional Monte Carlo simulations we show that our model correctly describes the distinct conduction properties of those materials, and in addition displays the critical behavior of both random-superconducting and random-resistor networks at two different critical concentrations.

Leaf aging and lipid peroxidation: The role of the antioxidants vitamin C and E

Abstract: To study age-related peroxidation in annual beech (Fagus silvatica Mill.) leaves and perennial fir (Abies alba Mill.) needles, the concentration changes of the antioxidants vitamin C (ascorbic acid) and vitamin E (α-tocopherol) present in leaves and needles were determined, and the formation of thiobarbituric acid reactants was measured as an index of age-related lipid peroxidation. With age, the content of the lipid-soluble antioxidant vitamin E increased, and the increase was higher in beech leaves than in fir needles. A comparable age-dependent increase of the vitamin C content was found neither in leaves nor in needles. The concentration ratio of the vitamin C to the vitamin E present in leaves and needles, which determines the potency of the anti oxidative system consisting of both vitamins, declined with age. This decline was directly related to a higher peroxidation of lipids. The extent of age-related peroxidative damage of cells seems to be controlled by the potency of anti oxidative systems.

Lagrangians forn point masses at the second post-Newtonian approximation of general relativity

Abstract: We study the effect of an infinitesimal coordinate transformation on the Lagrangian and on the metric functional of a system ofn point masses. We show how to compute the Lagrangians ofn point masses at the second postNewtonian approximation of general relativity in different coordinate systems. The Lagrangians are shown to depend on the accelerations except in a special class of coordinates. This class includes the coordinates associated with the canonical formalism of Arnowitt, Deser, and Misner, but excludes most other coordinate systems used in the literature (notably the harmonic one).

Identification of a voltage-dependent anion channel in the apical membrane of a Cl−-secretory epithelium (MDCK)

Abstract: An anion-selective channel of large unit conductance is present in apical membranes of a secretory epithelial cell. For cell-attached patch-clamp configuration on cultured MDCK cells channels with a conductance of about 460 pS are observed at 37° C. The channel becomes spontaneously activated only in rare cases. In inside-out membrane patches the probability of observing this type of channel increased significantly suggesting that the channel is controlled by an up to now unknown mechanism. The channel shows a voltage-dependent burst kinetic.

Inferior colliculus of the house mouse

Abstract: 1. Single unit responses were recorded from the dorsal cortex (DC), dorsomedial nucleus (DM) and central nucleus (CN) of the inferior colliculus (IC) of chlorprothixene anesthetized house mice. Tone and noise thresholds, spontaneous activities, frequency tuning curves, tone response patterns, spike rate-intensity functions, and tone-innoise response patterns were determined within a 40 dB sound intensity range above the units' thresholds. 2. Single unit thresholds were often lower than the average lowest behavioral thresholds, however, the envelope of the neural data resembled the behavioral curve in most of the frequency range (Fig. 2). 3. Spontaneous activity ranged from 0 to 62 spikes/s with a peak of the distribution at 1–3 spikes/s (Fig. 3). 4. About 35% of CN excitatory tuning curves were primary-like (resembling those of auditory nerve fibers). The remaining 65% were variable including broad, constant width, closed, tilted and complex shapes. The proportion of tuning curve shapes in the DC was similar to that in the CN, however the DM distribution, in which tuning curves with steep flanks and closed ones dominated, differed significantly from both (Figs. 4, 5). 5. Tonic, primary-like tone response patterns were found at least at some intensities in nearly 55% of units from all three nuclei (Fig. 8). The other response patterns observed were phasic, phasic with some tonic components, pauser, long latency, spontaneous activity inhibited, and no tone response (Figs. 7, 8). 6. With increasing sound intensity 60% of the units changed their tone response pattern, most frequently to pauser responses (Fig. 9). 7. Neurons from the three nucleus areas had significantly different shapes of rate-intensity functions (Fig. 10). Monotonic functions dominated in the CN, peaked ones in the DC and peaked and complex ones in the DM (Fig. 11). 8. Averaged spike rates of all IC units studied and averaged tendencies for rate increases or decreases changed little with increasing tone level from 10 to 40 dB above the units' tone thresholds. 9. Nine distinct tone-in-noise response patterns were seen when unit responses as a function of noise level were examined. Noise can have facilitating, enhancing, inhibitory, or little influence on the response patterns in tone intervals. In the intertone (noise only) intervals noise can have excitatory, inhibitory or no effects on the unit responses (Figs. 13, 14). Tone-in-noise response patterns depended both on tone and noise intensities and shifted frequently with changing stimulus intensity. Occurrence rates of the different tone-in-noise response patterns differed significantly between the DC and the DM or CN (Fig. 14). 10. Averaged across the different nuclei of the IC, about half of tone-in-noise responses differed from those described for the auditory nerve and ventral cochlear nucleus. 11. Tuning curve shapes correlated significantly with the forms of rate-intensity functions (primarylike tuning curves — non-peaked functions; higher order tuning curves — peaked or complex functions). There were also statistically significant relations between tone response patterns and tone-innoise response patterns. 12. Temporal response patterns of the neurons (PSTH patterns) were not related to tuning curve shapes and to forms of rate-intensity functions. 13. Results are discussed with regard to sound intensity effects on the processing of auditory information in the three IC nuclei and in comparison with studies on other mammals.

Degradation of unsaturated hydrocarbons by methanogenic enrichment cultures

Abstract: The biodegradability of hydrocarbons under anaerobic conditions was studied in enrichment cultures using mineral media inoculated with sewage sludge or sediment samples of limnic and marine origin No indication of methanogenic degradation was obtained with either n-hexane, n-hexadecane, n-heptadecane, 1-hexene, cis-2-hexene, trans-2-hexene, isoprene, 1-hexine, benzene, toluene, xylene, cyclohexene, cycloheptatriene, cyclopentadiene, styrene, naphthalene, azulene, or β-carotene Squalene was incompletely converted to methane and carbon dioxide Complete degradation was observed with 1-hexadecene Methanogenic subcultures were maintained on 1-hexadecene and squalene Both enrichments contained after several transfers Methanospirillum hungatei and Methanothrix soehngenii as prevalent methanogenic bacteria Acetate (⩽80 μM) was the only intermediary product detected indicating that degradation proceeded via hydrogen-dependent syntrophic β-oxidations Short rods on hexadecene and cocci on squalene were found to be associated with substrate degradation The results indicate that terminal double bonds can be sufficient to allow methanogenic degradation of hydrocarbons whereas branching and terminal ring closures may significantly contribute to hydrocarbon stability in anoxic environments

Consequences of iron deficiency on photosynthetic and respiratory electron transport in blue-green algae.

Abstract: Growth of Aphanocapsa in low iron media resulted in a decrease of the endogenous iron pool. Below a critical concentration photosynthetic electron transfer was specifically depressed. This was caused by a strong inhibition of the synthesis of cytochromes b-559 of PSII, cytochromes b-563, f-557, and the ‘Rieske’ Fe-S center of the cytochrome complex and especially the Fe-S centers of PSI. The influence of iron limitation on respiration and chlorphyll formation was negligible.

German norms for the Harvard Group Scale of Hypnotic Susceptibility, Form A.

Abstract: German norms for the Harvard Group Scale of Hypnotic Susceptibility, Form A (HGSHS:A) of Shor and E. Orne (1962) are presented. 3 samples (N = 108, N = 103, and N = 163) were pooled resulting in an aggregate sample of 374 Ss which was in general congruent with earlier normative studies (Laurence & Perry, 1982; Sheehan & McConkey, 1979; Shor & E. Orne, 1963) with regard to score distribution and item difficulty level. Reliability of the German adaptation of HGSHS:A was somewhat lower than the reliabilities reported by the 3 cited studies, but in terms of standard error of measurement (estimated for each study by using the corresponding reliability coefficient), the German and the other studies were quite comparable. Results show that HGSHS:A is a useful instrument for initial screening of hypnotizability in a German context.