Showing papers by "University of Konstanz published in 1979"

Reversible electrical breakdown of lipid bilayer membranes: a charge-pulse relaxation study.

Abstract: Charge-pulse experiments were performed with lipid bilayer membranes from oxidized cholesterol/n-decane at relatively high voltages (several hundred mV). The membranes show an irreversible mechanical rupture if the membrane is charged to voltages on the order of 300 mV. In the case of the mechanical rupture, the voltage across the membrane needs about 50–200 μsec to decay completely to zero. At much higher voltages, applied to the membrane by charge pulses of about 500 nsec duration, a decrease of the specific resistance of the membranes by nine orders of magnitude is observed (from 108 to 0.1 Ω cm2), which is correlated with the reversible electrical breakdown of the lipid bilayer membrane. Due to the high conductance increase (breakdown) of the bilayer it is not possible to charge the membrane to a larger value than the critical potential differenceV c. For 1m alkali ion chloridesV c was about 1 V. The temperature dependence of the electrical breakdown voltageV c is comparable to that being observed with cell membranes.V c decreases between 2 and 48°C from 1.5 to 0.6 V in the presence of 1m KCl. Breakdown experiments were also performed with lipid bilayer membranes composed of other lipids. The fast decay of the voltage (current) in the 100-nsec range after application of a charge pulse was very similar in these experiments compared with experiments with membranes made from oxidized cholesterol. However, the membranes made from other lipids show a mechanical breakdown after the electrical breakdown, whereas with one single membrane from oxidized cholesterol more than twenty reproducible breakdown experiments could be repeated without a visible disturbance of the membrane stability. The reversible electrical breakdown of the membrane is discussed in terms of both compression of the membrane (electromechanical model) and ion movement through the membrane induced by high electric field strength (Born energy).

Molecular Transformations in Sarcolasmic Reticulum of Fast‐Twitch Muscle by Electro‐Stimulation

Abstract: Chronic electro-stimulation of fast-twitch rabbit muscle with the frequency pattern received by a slow-twitch muscle induces a progressive transformation of the sarcoplasmic reticulum. After 2 days stimulation activities of Ca2+-dependent ATPase and of Ca2+ transport begin to decrease, and are paralleled by a progressive decrease in Ca2+-dependent and Ca2+, Mg2+-dependent phosphoprotein formation, reduced rate of dephosphorylation and a rearrangement of the electrophoretic polypeptide and phosphoprotein patterns. These findings suggest a transformation of the sarcoplasmic reticulum to resemble that of a slow-twitch muscle. This transformation is paralleled by increase in time-to-peak of twitch contraction and half relaxation time and occurs before conversion of the myosin light chain pattern is observed. The parallel time course of changes in contractile properties of stimulated muscle and the molecular and functional properties of the sarcoplasmic reticulum emphasizes the definitive role of the latter in determining the twitch characteristics of fast and slow twitch muscles.

Castration for sex offenders: treatment or punishment? A review and critique of recent European literature.

Abstract: The recent European literature on surgical castration in treatment of sex offenders is reviewed. Results are reported of the most important empirical studies conducted in this field of sex research in Germany, Switzerland, Norway, and Denmark. Methodological problems of follow-up studies on castrates as well as the subject of castration as treatment for sex offenders as a whole are discussed. The main conclusion is that there is no scientific or ethical basis for castration in the treatment of sex offenders.

Photocurrents generated by bacteriorhodopsin on planar bilayer membranes

Abstract: When purple-membrane fragments from Halobacterium halobium are added to one aqueous phase of a positively-charged black lipid membrane, the membrane becomes photoelectrically active. Under normal conditions the steady-state photo-current is extremely low, but increases considerably when the lipid bilayer is doped with proton-permeable gramicidin channels or with a lipophilic acid-base system. These findings indicate that the purple-membrane sheets are bound to the surface of the bilayer, forming a sandwich-like structure. The time-behaviour of the photocurrent may be interpreted on the basis of a simple equivalent circuit which contains the conductance and capacitance of the purple membrane in series with the conductance and capacitance of the lipid bilayer. From the dependence of the photocurrent on the polarization of the exciting light the average angle between the transition moment of the retinal chromophore and the plane of the bilayer was calculated to be about 28 degrees. Furthermore, it was shown that chromophore-free apomembrane binds to the lipid bilayer and that its photoelectrical activity can be restored in situ by adding all-trans-retinal to the aqueous phase.

Reception of particle oscillation in a medium — an unorthodox sensory capacity

Abstract: The oscillation of particles in a medium is the adequate stimulus for specialized receptors. Such receptors can be found in nearly all phyla in the animal kingdom. Specialized sensory hairs in arthropods are used here as an example to show conditions and limits of vibration reception in a medium. The use of this sensory capacity in biologically relevant situations is shown on some well-known examples.

Ascorbate oxidase from Cucurbita pepo medullosa. New method of purification and reinvestigation of properties.

Abstract: 1. Ascorbate oxidase has been isolated from the green squash Cucurbita pepo medullosa by a new purification method. Furthermore a low-molecular-weight copper protein containing one type-1 copper/20000 Mr could be separated during the purification of the oxidase. The six-step procedure developed improved the yield of ascorbate oxidase by a factor of 2.5. The method is well reproducible and a constant value of 8 Cu (7.95 +/- 0.1/140000 Mr) has been established. By ultracentrifugal and electrophoretic criteria the enzyme preparations have been found to be homogeneous. They exhibited a specific activity of 3930 +/- 50 units/mg protein or 1088 +/- 15 units/microgram copper. 2. The pure enzyme is characterized by the following optical purity indices: A280/A610 = 25 +/- 0.5, A330/A610 = 0.65 +/- 0.05 and A610/A500 = 7.0 +/- 0.25. The molar absorption coeffient of the characteristic absorption maximum at 610 nm (oxidized minus reduced) amounts of 9700 M-1 cm-1 . 3. Computer simulations of the electron paramagnetic resonance (EPR) spectra of the oxidized enzyme reveal the following parameters: for the type-1 (blue) copper gz = 2.227, gy = 2.058, gx = 2.036; Az = 5.0 mT, Ay = Ax = 0.5 mT, for the type-2 (non-blue) copper g parallel to = 2.242, g perpendicular = 2.053; A parallel to = 19.0 mT, A perpendicular 0.5 mT. Out of the eight copper atoms present in the oxidase four are detectable by EPR. Of these, three belong to the type-1 class, and one to the type-2 class, as demonstrated by computer simulations of the EPR spectra. 4. To achieve full reduction of the enzyme, as measured by bleaching of the blue chromophore, four equivalents of L-ascorbate or reductase must be added in the absence of molecular oxygen. Upon reduction of the enzyme the fluorescence at 330 nm (lambda max ex = 295 nm) is enhanced by a factor of 1.5 to 1.75. The reduced enzyme is readily reoxidized by dioxygen, ferricyanide or hydrogen peroxide. It binds two molecules of hydrogen peroxide in the oxidized state (1/type-3 Cu pair), which can be monitored by a characteristic increase of the absorbance around 310 nm (delta epsilon = 1000 +/- 50 M-1 cm-1). Corresponding changes in EPR and fluorescence spectra have not been detected.

Isolation of a spermatozoid-releasing and -attracting substance from female gametophytes of Laminaria digitata.

Abstract: SEVERAL dioecious marine brown algae have been valuable in studying chemical communication during sexual reproduction. For example, female gametes of Ectocarpus siliculosus, Cutleria multifida and Fucus serratus secrete olefinic hydrocarbons into the seawater to attract male gametes1–3. A more complex system is found in the order Laminariales, which includes the large kelps. Mature female gametophytes in members of this group secrete highly volatile material with spermatozoid-attracting activity, which also induces explosive discharge of antheridia4. We report here a study of this volatile material. It is now possible to attribute spermatozoid-releasing and -attracting activity to one specific compound.

Microphotometric studies on intraacinar enzyme distribution in rat liver.

Abstract: Intraacinar distribution of succinate dehydrogenase (SDH), malate dehydrogenase (MDH), NADP-dependent isocitrate dehydrogenase (IDH), glutamate dehydrogenase (GluDH), lactate dehydrogenase (LDH) and NADH-tetrazolium dehydrogenase (TR) was studied in rat liver cryostat sections by multipositional microphotometric activity determinations. By statistical evaluation, activity of individual enzymes could be related to the acinar topography. Activity was evaluated with regard to distance of measuring position either from afferent (portal) or efferent (hepatic) vessels. Two independent distribution curves were obtained for each enzyme. Acinar distribution of all the enzymes studied followed sigmoid courses with maximal activity of SDH, MDH and LDH in zone 1 ("periportal") and GluDH, IDH, TR in zone 3 ("pericentral"). For all enzymes, maximum activity gradients were confined to zone 2 of the acinus. Data were also evaluated as ratios of activities in zone 1 and zone 3. The following ratios zone 1/zone 3 were obtained: SDH = 1.9, MDH = 1.7, IDH = 0.5, GluDH = 0.5, LDH = 1.3 and TR = 0.6.

Metabolic heterogeneity of muscle fibers classified by myosin ATPase

Abstract: Muscle fibers re commonly classified histochemically into three types by the staining intensity for myosin ATPase combined with those for metabolic enzymes. Preincubation at pH 4.6 gives rise to three staining intensities of myosin ATPase which are also used for fiber typing. The two classification systems were compared by computer analysis of the individual staining profiles of over 2,500 fibers, and found not to be equivalent. The analysis showed metabolic heterogeneity among the fiber groups distinguished according to their differences in myosin ATPase.

On the Photopotential Output of Electrochemical Solar Cells Based on Layer‐Type d‐Band Semiconductors

Abstract: A comparative study of molybdenum- and tungsten-dichalcogenides in contact with various redox electrolytes revealed that in absolute values as well as in relation to the energy gap, n-type WSe2 is producing the largest photopotential output. It exceeds 0.55 Volt in presence of several redox couples (Fe2+/3+, H2Q/Q pH = 10, Fe(CN)3-/4-, 6, Ru3-/4+, Br−/Br2, Ce3+/4+) and amounts to more than 0.7 Volt in presence of I−/I2. Addition of small quantities of iodide can increase the photopotential output in presence of redox systems with lower redox potential by up to 0.1 Volt. This gives further evidence for the specific photochemical surface activity of iodide on layer-type electrodes and is an example for the influence of surface states on the efficiency of energy conversion. - The higher photopotential output of WSe2 as compared to that of MoSe2 (maximum value I−/I2:0.56 Volt) is explained in terms of a negative shift of the conduction band edge. With respect to the efficiency of electrochemical solar energy conversion WSe2 is considered to be the most promising compound among layer-type d-band semiconductors. Eine vergleichende Studie von Molybdan- und Wolframdichalkogeniden in Kontakt mit verschiedenen Redox-Elektrolyten ergab. das, in absoluten Werten wie auch im Verhaltnis zur Energie-Lucke, n-leitendes WSe2 das hochste Photopotential liefert. Es ubertrifft 0,55 Volt in Gegenwart von mehreren Redox-Paaren (Fe2+/3+, Hydrochinon/Chinon (pH = 10), Fe(CN)3-/4-, 6, Ru3-/4+, Br−/Br2, Ce3+/4+) und betragt mehr als 0,7 Volt in Gegenwart von I−/I2. Zugaben von kleinen Mengen von Jodid konnen in Gegenwart von Redox-Systemen mit niedrigerem Redox-Potential das Photopotential um bis zu 0,1 Volt erhohen. Das ist ein weiterer Hinweis auf die spezifische photochemische Oberflachenaktivitat von Jodid an Schichtgitter-Elektroden und ein Beispiel fur den Einflus von Oberflachenzustanden auf die Wirksamkeit der Energieumwandlung Das im Vergleich zum MoSe2 (Maximalwert: I−/I2: 0,56 Volt) hohere Photopotential von WSe2 wird durch eine negative Verschiebung des Leitungsbandes erklart. Im Hinblick auf die Wirksamkeit der elektrochemischen Sonnenenergieumwandlung wird WSe2 als die vielversprechendste Verbindung unter den schichtartigen d-Band-Halbleitern angesehen.

Quantitative analysis of nerve fibre densities in the cochlea of the house mouse (Mus musculus).

Abstract: Transverse sections of the cochlear nerve, silver-stained surface preparations of the cochlea, and silver- and osmium-stained tangential sections of the cochlea of the house mouse were made to determine the number and density of nerve fibres entering the organ of Corti and their distribution to inner and outer hair cells along the cochlear spiral. A number of 12,578 +/- 819 fibres was counted within the cochlear nerve, which is almost equal to the total number of 12,350 +/- 810 fibres entering the organ of Corti. The 12,350 fibres divide into 9,780 (= 79%) fibres running to the inner hair cells, 703 (= 6%) basilar (afferent) fibres and 1,867 (= 15%) upper tunnel radial (efferent) fibres innervating the outer hair cells. About 93% of all afferent fibres are connected to the inner hair cells, and only 7% innervate outer hair cells. The density of fibres running to the inner hair cells varies considerably and has a significant (p less than 0.01) absolute and relative maximum 3.7 mm and 2.9 mm from the apex respectively (total length: 6.84 mm) and decreases toward apex and base. The density of afferent fibres running to the outer hair cells shows a slow increase up to 2 mm from the apex, and remains on a constant low level (5.5 fibres per 40 micrometer) down to the base. The density of efferent fibres running to the outer hair cells increases linearly up to about 2 mm from the apex, remains rather constant (10 fibres per 40 micrometer) from 2 mm to 4 mm, and then decreases toward the base. Generally, the outer hair cells show a convergent innervation pattern, the inner hair cells a divergent one. The significance of the present measurements is discussed in relation to respecitve results from other mammals and in relation to auditory thresholds.

Electric and Motor Responses of the Weakly Electric Fish, Gnathonemus petersii (Mormyridae), to Play-back of Social Signals

Abstract: 1. Seven isolated G. petersii resting in their daytime hiding-places were stimulated via a dipole model (Fig. 1a) with previously tape-recorded electric organ discharge (EOD) patterns in an attempt to determine whether G. petersii distinguishes two different intraspecific EOD patterns, rest and attack. 2. Rest pattern A was characterized by a broad distribution of EOD intervals, a low mean discharge rate (8 Hz, Fig. 3), and a long period of significantly positive autocorrelation (2 s, Fig. 4a). Accordingly, the spectrum of EOD rate fluctuations showed a low frequency range (0.005 to 0.12 Hz, Fig. 5a). Attack pattern B was a considerably different EOD interval distribution of high mean discharge rate (25 Hz, Fig. 3), showing a short period of significantly positive autocorrelation (0.8 s, Fig. 4b), only. Here, the spectrum of EOD rate fluctuations was at a considerably higher frequency range (0.09 to 0.47 Hz, Fig. 5b). 3. Play-back of attack pattern B elicited significantly more bodily startle responses from the experimental fish (Fig. 6) than did the rest pattern A (Table 1). Also the number of attacks directed at the dipolemodel was significantly greater during stimulation with attack pattern B (Table 2, Fig. 6). 4. The EOD responses of the experimental fish differed in several respects depending on which stimulation pattern was used. The modes of the pulse rate histograms as well as their spans were lower during play-back of rest pattern A than during stimulation with attack pattern B (average 12.3 vs 16.2 Hz, and average 47 vs 56 Hz, respectively; Fig. 11). Shortterm (0.2 s) EOD rate correlations were stronger when the fish were stimulated with rest pattern A than when they were stimulated with attack pattern B (average correlations 0.67 and 0.61, respectively; Figs. 10 and 11). Significant positive correlations were maintained for longer periods of time during rest pattern stimulation than during attack pattern stimulation (average 1.94 and 1.24 s, respectively; Figs. 10 and 11). The spectra of EOD rate fluctuations of the stimulated fish were at lower frequency ranges during rest pattern stimulation than during attack pattern stimulation (average amplitude-spectrum peak frequencies 0.02 and 0.07 Hz, respectively; Figs. 12 and 13). 5. Although maximal cross-correlations from the EOD rates to the stimulus pulse rates were weaker during rest pattern stimulation (average 0.2) than during attack pattern stimulation (average 0.33), significant cross-correlations were maintained for longer periods of time during rest pattern stimulation than during attack pattern stimulation (average 1.78 and 0.92 s, respectively). The lags of maximal cross-correlations were greater during rest pattern stimulation than during attack pattern stimulation (average 2.6 and 0.8 s, respectively; Figs. 14 and 15). 6. The results clearly showed that at least two specific EOD time patterns encode different ‘messages’ in the intraspecific communication system of G. petersii.

Activities of malate dehydrogenase, 3-hydroxyacyl-CoA dehydrogenase and fructose-1,6-diphosphatase with regard to metabolic subpopulations of fast- and slow-twitch fibres in rabbit muscles

Abstract: Activities of malate dehydrogenase (MDH), 3-hydroxyacyl-CoA dehydrogenase (HAD) and fructose-1,6-diphosphatase (FDPase) were determined in single fibres dissected from freeze-dried rabbit psoas and soleus muscles. Slow-twitch fibres as determined by qualitative ATPase reaction represent a rather uniform population with regard to HAD and MDH activities. In these fibres the two enzymes are in constant proportions. FDPase is found at extremely low activities in slow-twitch fibres and because of its relatively high activity in fast-twitch fibres of soleus and psoas muscle it might be used as a marker enzyme. Fast-twitch fibres in psoas muscle represent a heterogeneous population with regard to activities of MDH as well as of HAD. The two enzyme activities are not proportional in fasttwitch psoas fibres. These findings suggest the existence of metabolic sub-populations of fast-twitch fibres having a wide range of aerobic oxidative capacities and having differences in their capacity to oxidizing fatty acids.

Independent Development of Contractile Properties and Myosin Light Chains in Embryonic Chick Fast and Slow Muscle

Abstract: 1. The contractile speeds and tetanus/twitch ratios of the slow anterior latissiumus dorsi (ALD) and fast posterior, latissimus dorsi (PLD) muscles were studied during embryonic development and correlated with the type of myosin light chains present in these muscles as studied by one and two dimensional polyacrylamide gel electrophoresis. 2. At a time when the contractions of PLD were slow, i.e. in 15 day old embryos, the myosin light chains in this muscle were of the fast type. The slow contraction of this muscle may be due to incomplete and slow activation of the contractile elements. The tetanus/twich ratio of muscles from 15 day old embryos is low and increases sharply with age. This increase could be due to the maturation of the internal membrane system, and occurs at about the same time as the increase in the speed of contraction. 3. ALD muscles contract slowly during all stages of development, although their tetanus/twitch ratio also increases with age. At 13 days they contain a mixture of fast and slow type myosin light chains and with increasing age the proportion of the slow type myosin light chains increases at the expense of the fast type. The slow time course of contraction of ALD is consistent with the presence of slow type myosin light chains. 4. The possibility that the synthesis of the slow type myosin light chains in ALD is induced by early motor activity in chick embryos is discussed.

Fluorescence Properties of Reduced Flavins and Flavoproteins

Abstract: Fluorescence lifetimes and polarized emission properties of reduced flavin were measured using several model compounds and flavoproteins. Depending on the conditions of solvent and temperature or reduction method the lifetimes vary between 1 and 15 ns. The longer lifetime values are found in several forms of reduced lactate oxidase, in which a good correlation exists between fluorescence intensity and lifetime. In practically all flavoproteins the fluorescence is heterogeneous. Several mechanisms are proposed to explain the observed heterogeneity in lifetimes. The reduced models in glycerol at subzero temperature exhibit high degrees of polarization of the fluorescence, whereas distinct depolarization is encountered in several reduced flavoproteins suggesting a certain mobility of the flavin chromophor.

The prefrontal cortex: Projection area of the thalamic mediodorsal nucleus?

Abstract: The historical bases of the definitions of the prefrontal cortex are reviewed (cytoarchitecture, electrical unexcitability, afferents from the mediodorsal thalamic nucleus). Evidence is presented that the widely accepted proposal of Rose and Woolsey (1948) to name all cortex prefrontal that is reached by afferents from the mediodorsal nucleus is questionable for three reasons: the diversity of cortical fields reached by the mediodorsal nucleus, the overlapping of thalamic projections, and the possibility of a column- or band-like thalamocortical organization. An alternative approach to a definition of the prefrontal cortex is suggested.

On the resistivity due to two-level systems in metallic glasses

Abstract: We consider the electrical resistivity due to the two-level systems which have been detected recently by ultrasonic saturation experiments. Using model parameters consistent with these experiments, we calculate a temperature-dependent resistivity. It is found that the scattering mechanism is too weak by at least three orders of magnitude to account for experimental observations.

Kinetic microphotometric activity determination in enzyme containing gels and model studies with tissue sections

Abstract: The dependence of microphotometrically recorded reaction rate on local enzyme concentration was studied as a basic prerequisite of comparative microphotometric enzyme activity determinations at initial rate conditions in tissue sections. Polyacrylamide gels containing defined concentrations of glucose-6-phosphate dehydrogenase served as a model. Optimal conditions of preparing enzyme containing gels are reported. Measurements in which either thickness of gel sections or enzyme concentration was varied proved the linear relationship between local enzyme concentration and microphotometrically recorded reaction rate. Sections of enzyme containing gels as well as cross-sections of rat muscles were used as models for studying possible influences of heterogeneous chromophore distribution (distributional error). No such influences could be detected during the initial phase of the staining reaction which suggests that distributional error is of no significance for kinetic microphotometric enzyme activity determination at initial rate conditions.

Hormonal Regulation of Glucokinase in Primary Cultures of Rat Hepatocytes

Abstract: Glucokinase activity in rat hepatocyte cultures declined with a half-time, t1/2, of 32 h during 3 days under serum-free conditions. Addition of insulin and triamcinolone to the culture medium prevented this decay. Glucokinase levels in hepatocytes derived from fasted rats could be elevated from 7.4 to 16.4 mU/mg protein in the presence of insulin and triamcinolone. In 2-day-old cultures glucokinase was induced in the presence of both hormones with a half time, t1/2, of 5.1 h. In cultures treated for 2 days with triamcinolone, insulin induced a 80% increase of glucokinase even in the absence of glucocorticoids. Insulin induction was dependent on protein synthesis but occurred in the absence of RNA synthesis. Glucocorticoid action, however, depended on RNA synthesis suggesting that glucocorticoids control transcription. Insulin evoked half-maximal effects at 3 nM and dexamethasone and triamcinolone at 0.1 and 1 nM respectively. Degradation of glucokinase was initiated in 2-day-old hepatocytes after removal of triamcinolone and insulin. Protein synthesis was essential for the onset of degradation and glucagon did not affect the rate of glucokinase degradation.

Muonium states in germanium

Abstract: An anomalous muonium state similar to that in silicon has been found in germanium. This state can be described an anisotropic hyperfine interaction with the parameters $\frac{{A}_{\ensuremath{\perp}}}{h}=130.7\ifmmode\pm\else\textpm\fi{}1$ MHz and $\frac{{A}_{\ensuremath{\parallel}}}{h}=26.8\ifmmode\pm\else\textpm\fi{}1$ MHz. In contrast to Si this anomalous muonium state in Ge was not observed at low external fields. In addition, a detailed investigation of normal muonium in Ge was carried out. For undoped Ge the hyperfine constant is found to be temperature independent in the range between 6 and 81 K with an average value of $\frac{A(\mathrm{Ge})}{h}=2361\ifmmode\pm\else\textpm\fi{}3$ MHz or $\frac{A(\mathrm{Ge})}{A(\mathrm{vac})}=0.5290\ifmmode\pm\else\textpm\fi{}0.0007$. The present value is considerably lower than that published by Gurevich et al. The relaxation rate of normal muonium in the Ge sample investigated increases sharply above about 50 K with an activation energy of 14 meV. A correlation with the thermal activation of impurity charge carriers is suggested.