Showing papers by "University of Freiburg published in 1972"

Differentiation of the transmembrane Na and Ca channels in mammalian cardiac fibres by the use of specific inhibitors

Abstract: According to earlier studies on mammalian papillary muscles, verapamil and compound D 600 (a methoxy-derivative of verapamil) can abolish the Ca dependent contractile responses completely whilst the Na dependent action potentials persist. In an attempt to clarify the mechanism of action separate measurements of the transmembrane Na and Ca currents have been performed on ventricular trabeculae of cats using a special voltage clamp technique. The following results were obtained: As a functional significance of this dual membrane transport system it is possible to change the contractile force by inotropic substances which act on the Ca conductivity without a corresponding influence on excitation.

In-vitro auxin binding to particulate cell fractions from corn coleoptiles.

Abstract: When low concentrations (e.g. 10-6 M) of labelled 3-indoleacetic acid (14C-IAA) or α-naphthaleneacetic acid (14C-NAA) are added in vitro to homogenates of corn coleoptiles, radioactivity is reversibly bound to pelletable particles. From the saturation kinetics of the binding it is possible to estimate an apparent K M between 10-6 M and 10-5 M and a concentration of specific sites of 10-7–10-6 M per tissue volume. The binding is auxin-specific. Among many compounds tested, only auxins and such auxin analogues that are known to interact directly with auxin in transport and/or growth were found to interfere with this binding. For instance, the growth-active d-dichlorophenoxyisopropionic acid at 10-4 M inhibits 14C-NAA binding more than the less active l-isomer. The auxin-binding fractions are practically free of DNA and cytochrome-C oxidase and contain binding sites for 1-naphthylphthalamic acid. The results are discussed in context with the hyothesis—derived mainly from physiological data—that auxin receptors are localized at the plasma membrane.

Zur spektralen Unterschiedsempfindlichkeit der Honigbiene

Abstract: 1. Die im Dressurexperiment gemessene spektrale Empfindlichkeitskurve der Honigbiene ist dreigipfelig, was die Ergebnisse von Thomas und Autrum (1965) bestatigt. Die Maxima liegen etwa bei den Wellenlangen 345 nm (Ultraviolett), 440 nm (Blau) und 550 nm (Gelbgrun), vgl. Abb. 11. 2. Die Kurve der spektralen Unterschiedsempfindlichkeit der Biene weist zwei Optima auf, die etwa bei den Wellenlangen 400 nm (Violett) und 500 nm (Blaugrun) liegen (Abb. 18, 19). Im empfindlichsten Bereich des Unterscheidungsvermogens, im Blaugrun, wurden unter den gegebenen Versuchsbedingungen von der Biene noch Wellenlangen-Differenzen von 4,5 nm mit einer Anflughaufigkeit von 70% unterschieden. Der spektrale Verlauf der Parbton-Unterscheidung last sich am besten unter der Annahme eines trichromatischen Farbsystems verstehen, insbesondere zeigen die Ergebnisse, das das farbauswertende System der Biene die Daten nur eines Blaurezeptor-Typs verwendet.

Tubular and filamentous structures in pollen tubes: Possible involvement as guide elements in protoplasmic streaming and vectorial migration of secretory vesicles

Abstract: An ultrastructural study of the pollen tubes of Lilium and Clivia has demonstrated three different classes of longitudinal structures which could influence patterns of protoplasmic streaming and/or serve as “guide elements” in the vectorial migration of secretory vesicles: (a), cortical and noncortical microtubules; (b), microfilaments; and (c), subcortical tubules and cisternae of the endoplasmic reticulum (“subsurface cisternae”) Morphological details of these structures are described Colchicine concentrations which lead to the complete disappearance of the microtubules affect neither germination of the pollen nor cytoplasmic streaming and tip growth of the elongating pollen tubes Tip growth is initially uninhibited by cycloheximide, and cytoplasmic streaming is insensitive to this inhibitor However, both of these processes are sensitive to cytochalasin B and vinblastine Our results suggest that neither microtubules nor subsurface cisternae are essential for cytoplasmic streaming and directional secretion of cell surface materials in the pollen tube but would be consistent with an involvement of microfilamentous structures in these processes Additionally, the possible importance of the lateral cross-link elements interconnecting all three types of structures is discussed

Gesang des Männchens und Lautschema des Weibchens bei der FeldheuschreckeChorthippus biguttulus (Orthoptera, Acrididae)

Abstract: 1. Der Gesang der FeldheuschreckeChorthippus biguttulus ist ein charakteristisch amplitudenmoduliertes Lautmuster (Abb. 2): Der Spontangesang besteht aus 1–5 (meist 3) Versen und jeder Vers aus 20–60 Silben (u.a. Faber, 1929). Die Silben sind ihrerseits aus Pulsen aufgebaut, was besonders im Gesang einseitig amputierter Mannchen deutlich zu erkennen ist, und zwar bis auf seltene Ausnahmen stets aus einer geraden Anzahl. Nach der Zahl der Pulse (4, 6 oder 8, selten auch mehr) kann man verschiedene Silbentypen unterscheiden. Die Silbenund Pausendauern sind bei einer vorgegebenen Temperatur wenig variabel (Abb. 3, 4, 5). Der „Werbewechselgesang” unterscheidet sich im zeitlichen Muster der Silben- und Pausendauern nicht vom Spontangesang. 2. Mit steigender Temperatur verkurzen sich sowohl die Dauern der verschiedenen Silbentypen als auch die Pausendauern nach einer Exponentialfunktion. Das Verhaltnis zwischen Silben- und Pausendauer bleibt dabei konstant (Abb. 6, 7, 8). 3. Das Lautschema (angeborener auslosender Mechanismus des Weibchens fur die Antwort auf den Gesang eines Mannchens) bleibt wahrend der Lebensdauer eines Weibchens konstant. Eine Lautattrappe aus getastetem Rauschen lost nur dann eine Antwort aus, wenn die Parameter Silben- und Pausendauer bestimmte, voneinander abhangige Werte annehmen: Mit steigender Silbendauer wird auch die am besten beantwortete Pause langer (Abb. 14). Tragt man die optimal beantwortete Pausendauer als Funktion der Silbendauer auf, so erhalt man annahernd eine Gerade (Abb. 15). Versdauer, Versabstand und Verszahl spielen beim Erkennen des Artgesanges nur eine untergeordnete Rolle, jedoch mus eine Mindestversdauer von etwa 1,2 s eingehalten werden (Abb. 18). Die Abstande zwischen den Pulsen durfen (unter den gegebenen Versuchsbedingungen) 1–2 ms nicht uberschreiten, soll das Muster seine Wirksamkeit nicht verlieren. Bei langeren Pulsen ist auch die tolerierte Pulspause groser (Abb. 19). 4. Das Lautschema ist temperaturabhangig. Bei niedrigerer Temperatur werden bei einer gegebenen Silbendauer langere Pausen maximal beantwortet und insgesamt langere Silben bevorzugt (Abb. 15, 20). 5. Das Lautschema eines Weibchens umfast bei einer Temperatur von 35 ° C nicht nur die Gesangsmuster von Mannchen derselben Temperatur, sondern die Silben-Pausen-Muster eines weiten Temperaturbereiches (Abb. 17, 21).

Angular Distribution of Auger Electrons Following Photoionization

Abstract: It is shown that the photoionization process of inner-shell electrons by unpolarized radiation leads to an alignment of the ionized atoms. From the nonisotropic angular distribution of the following Auger electrons the relative partial photoionization cross sections can be determined.

The interphase distribution of satellite DNA-containing heterochromatin in mouse nuclei.

Abstract: The distribution of sites capable of binding mouse satellite-complementary RNA in the cytological hybridization reaction has been examined in mouse liver and testis interphase nuclei. The approach taken has been to combine hybridization with semi-thin sectioning and autoradiography in order to obtain a clear picture of the relationship of satellite DNA-containing structures to the rest of the interphase nucleus. In liver nuclei, hybridization occurs primarily with blocks of heterochromatin associated with the nuclear envelope. The most prominent of these, in terms both of size and intensity of hybridization, is the nucleolar stalk and the rest of the nucleolus-associated heterochromatin. The nucleolar body itself is not labeled, nor is much of the peripheral condensed chromatin ; in fact, a polarized distribution of satellite DNA is evident. In Sertoli and spematid nuclei, satellite DNA is found in a small number of large heterochromatin blocks with which the nucleolus is associated; some of this material bears a relationship to the nuclear envelope in these cells also.

IgM antibodies to Epstein-Barr virus in infectious mononucleosis.

Abstract: IgM antibodies to Epstein-Barr virus (EBV) could be demonstrated by immunofluorescence in the sera of all patients with clinical infectious mononucleosis (IM) and a heterophile antibody titer of ⩾40. The EBV-IgM antibodies were found only over a period of 2 to 3 months after onset of symptoms. Demonstration of IgM antibodies in the sera of patients therefore indicates recent infection and may be useful for diagnosis. The fact that EBV-IgM antibodies can only be demonstrated during a relatively short period supports the assumption that EBV is indeed the etiologic agent of IM.

The π‐Orbital Sequence in Norbornadiene and Related Hydrocarbons

Abstract: A method outlined previously [1] is used to show that in norbornadiene (3) the b2(π) orbital lies above a1(π), as predicted by theory. This indicates that in 3 through-space interaction between the two basis π-orbitals πa and πb is more important than through-bond interaction. Analysis of the PE.-spectra of 8-isopropylidene-tricyclo[3.2.1.02,4]-octane (13) and the corresponding octene (15) confirms that the π-orbital πc of the exocyclic double bond conjugates more strongly with the symmetric Walsh-orbital es of the cyclopropano moiety than with the π-orbital πa of a double bond in the same position.

The function of the aleurone layer during galactomannan mobilisation in germinating seeds of fenugreek (Trigonella foenum-graecum L.), crimson clover (Trifolium incarnatum L.) and lucerne (Medicago sativa L.): A correlative biochemical and ultrastructural study.

Abstract: The reserve endosperm galactomannans of fenugreek (Trigonella foenum-graecum L.), crimson clover (Trifolium incarnatum L.) and lucerne (Medicago sativa L.) are broken down to free galactose and mannose in dry-isolated endosperms (devoid of embryo) incubated under germination conditions. Breakdown is prevented by inhibition of protein synthesis or of oxidative phosphorylation in the aleurone layer. Resting aleurone cells contain inter alia a large number of ribosomes more or less regularly distributed in the ground plasma. At the onset of germination, before galactomannan breakdown begins, polysomes are formed and seem, at least partly, to become associated with vesicles and flat cisternae both probably newly formed and derived from ER. Concurrently with galactomannan breakdown in the reserve cells, wall corrosion occurs in the aleurone layer, the contents of the aleurone grains disappear and the rough vesicles and cisternae proliferate. Later a large central vacuole is formed which incorporates smaller vacuoles emerging from the cytoplasm, and at the same time the rough ER vesicles and cisternae become highly distended.It is concluded that the cells of the aleurone layer are responsible for the synthesis and secretion into the storage cells of the enzymes necessary for galactomannan degradation. The physiology of galactomannan breakdown is compared and contrasted with that of starch mobilisation in the endosperm of germinating cereal grains.

Determination of different cytomegalovirus immunoglobulins (IgG, IgA, IgM) by immunofluorescence

Abstract: Cytomegalovirus (CMV) immunoglobulins were determined by immunofluorescence. CMV IgM-antibodies usually reach relatively high titers soon after infection and can be detected in the blood of patients 2–8 months post infection. This confirms the experience that demonstration of CMV-IgM-antibodies is a suitable indicator of recent infection. CMV-IgM-antibodies were found in cases of clinical infectious mononucleosis.

Colchicine-binding Proteins in Chromatin and Membranes

Abstract: THE cytoplasm of several cell types contains a protein which is characterized by its specific capability to bind colchicine1–4 and which may be in dynamic equilibria between monomers and a distinct form of polymer structure, the microtubules. Studies of the character of this protein have hitherto usually proceeded from the cellular homogenate to the 100,000g supernatant which, at least in brain tissue, provides the largest enrichment and recovery. Two lines of observations prompted us to examine the possibility that colchicine-binding proteins exist in association with structures other than microtubules. First, considerable amounts of colchicine-binding protein are recovered in the 100,000g sediments. This is especially noticeable with mammalian liver but has also been noted during vertebrate brain fractionation4–7. Second, certain structures exhibit frequent and conspicuous associations with microtubules, in particular membranes8,9 and chromosomal structures. Membrane preparations too have been reported to share some protein properties in common with tubulin10,11.

The variation of photoelectron angular distributions with energy

Abstract: Photoelectron angular distributions for the ionization of the outerp-shell of the rare gases Ar, Kr, and Xe, and of the outerS- andd shell of Hg, are measured at various photon energies obtained from rare gas resonance radiation. The distributions are found to agree with the theoretically predicted form. Values of the anisotropy parameter β are determined, and their dependence on electron energy is compared with available numerical results, as well as with model calculations performed in this work. In the case of Hg the possible influence of spin-orbit coupling on the β-values is discussed.

The ultrastructure of the nuclear envelope of amphibian oocytes

Abstract: In order to investigate the chemical composition of the nuclear pore complexes isolated nuclei from matureXenopus laevis oocytes were manually fractioned into nucleoplasmic aggregates and the nuclear envelopes. The whole isolation procedure takes no more than 60–90 sec, and the pore complexes of the isolated envelopes are well preserved as demonstrated by electron microscopy. Minor nucleoplasmic and cytoplasmic contaminations associated with the isolated nuclear envelopes were determined with electron microscopic morphometry and were found to be quantitatively negligible as far as their mass and nucleic acid content is concerned. The RNA content of the fractions was determined by direct phosphorus analysis after differential alkaline hydrolysis. Approximately 9% of the total nuclear RNA of the matureXenopus egg was found to be attached to the nuclear envelope. The nonmembranous elements of one pore complex contain 0.41×10−16 g RNA. This value agrees well with the content estimated from morphometric data. The RNA package density in the pore complexes (270×10−15 g/μ3) is compared with the nucleolar, nucleoplasmic and cytoplasmic RNA concentration and is discussed in context with the importance of the pore complexes for the nucleo-cytoplasmic transport of RNA-containing macromolecules.

Autoregulation of contractility in the myocardial cell. Displacement as a controlling parameter.

Abstract: An investigation was carried out on isolated cat's papillary muscle in order to study displacement effects upon the intensity and the time course of the contractile activity. Displacements occurring before or very early during a contractile cycle produce effects which can be entirely explained on the basis of the cardiac active length-tension relation. Displacements occurring later exhibit additional effects in so far as either stretches or releases induce a drop of contractile activation such that the course of the subsequent tension development is markedly below that of the same displacement applied earlier. In order to separate these effects from those based on the active length-tension correlation experiments were performed in which very short release-stretch or stretch-release operations were applied so that the muscle length was virtually the same at the beginning and at the end of the operation. The results obtained under these conditions can be summarized as follows. The extend to which contractile tension drops after a stretch-release or a release-stretch cycle has been applied depends upon (1) the stimulus intervention interval (2) the length change performed (3) the velocity of displacement during the intervention. It is not dependent on the initial muscle length. Increasing the extracellular Ca-concentration considerably reduces the displacement effects. The results are tentatively explained by assuming an internal feedback loop between a variable of the contractile machinary and the preceding mechanism of activation.

Cytochalasin stops tip growth in plants

Abstract: Th ioha rns to f f w i rk t bei v ie len S a m e n k e i m u n g s f 6 r d e r n d [1]. Bei pos i t iv pho tob l a s t i s chen S amen k a n n er oft das L i ch t erse tzen, so dab S a m e n anch i m D u n k e l n ke i men [2]. Bei den n e g a t i v pho tob l a s t i s chen S a m e n yon Phacelia h e m m t Thioha rns to f f die K e i m u n g i m D u n k e l n s chwach u n d verst&rkt die 1 4 e i m n n g s h e m m u n g du rch L ich t [3]. Hier wird yon einer f6 rde rnden W i r k u n g auf die L i c h t k e i m u n g der nega t iv pho to b las t i schen [4] S a m e n von Zygophyllum coccineum L. ber ichter . Die S a m e n w u r d e n in W a d i Hof in der &gypt isch-arabischen Wi i s te im Sep tember 1970 ge sammel t . Zur K e i m u n g k a m e n sie bei 25 ~ in Pe t r i scha len (50 S a m e n pro Schale) auf eine Lage Fi l terpapier , die m i t 5 ml dest. W a s s e r oder der T h i o h a r n s t o f f L 6 s u n g getr&nkt war. Be l ich te t wurde mi t We ig l i ch t in e inem L i c h t s c h r a n k ( K I ( B 600L der Fa. Heraeus , H a n a u ; Leuch ts to f f rShren , Licht intensi t~i t in H6he d e r Schalen ca. 2 0 0 0 L u x ) . Jeder Ansa t z wurde 6fach durchgef t ih r t u n d die Ergebnisse gemi t te l t . Der P rozen t s a t z der geke imten S a m e n wurde fiber 7 Tage in 24s t f ind igem A b s t a n d festgestel l t , wobei als geke imt S a m e n gal ten, deren Ke imwurze l eben s i ch tba r geworden war. A m E n d e des Versuchs w u r d e die L~nge des H y p o c o t y l s und der Wurze l ermi t t e l t .

Orientation specificity of visual cortical neurons after head tilt.

Abstract: The orientation specificity of the receptive fields of single neurons in primary visual cortex of the cat varied as a function of sustained head tilt in a sample of 33 cells. The types of variation suggested analogies to certain psychophysical phenomena. Orientation specificity of visual cortical cells may in part be determined by information from non-visual afferent systems.

Relationship between growth of parsley and soybean cells in suspension cultures and changes in the conductivity of the culture medium.

Abstract: Changes in conductivity and pH during the growth cycle of cell suspensions derived from parsley (Petroselinum hortense) and soybean (Glycine max) have been investigated. Measurement of the conductivity of the medium represents a simple, rapid, and reliable method for the precise determination of the growth phase of a culture. The accuracy of this method has been tested by using phenylalanine ammonia-lyase, an enzyme that has a characteristically short, distinct period of activity during the growth cycle of soybean cell suspensions. It is suggested that an automatic regulation of the conductivity of the medium might be employed for growing plant cells in a continuous culture at a defined stage of growth.

Phytochrome-mediated Induction of Phenylalanine Ammonia-Lyase in Mustard Seedlings: A Contribution to Eliminate Some Misconceptions.

Abstract: The present report shows that the effect of red and far red light on the synthesis of phenylalanine ammonia-lyase can be ascribed to the action of phytochrome Pfr. This is true not only for short term irradiation but also for the action of continuous far red light. In the latter case, the model worked out by Hartmann implicating some excited species of phytochrome has to be taken into account.

Initial phases of gravity-induced lateral auxin transport and geotropic curvature in corn coleoptiles.

Abstract: Wild-type corn coleoptiles showed an initial downward bending upon transfer from the vertical to the horizontal position. Strong upward curvature started only 15–30 min after the begin of horizontal exposure.