Untersuchungen über die Bindung pflanzlicher Wuchsstoffe an verschiedene Komponenten des Chromatins in vitro

Summary Several growth substances (IAA, -NAA) are able to reduce thermal stability of artificially reconstituted nucleoproteins without splitting off measurable amounts of protein from DNA. This effect is not shown by substances structurally related to auxins (-NAA, tryptophan), but other growth substances (GA, KI) also reduce thermal stability of several reconstituated nucleoproteins.The effect of growth substances on the Tm of nucleoproteins strongly depends upon the concentration of the growth substances. The effective concentrations of IAA are lowered by increasing acidity of the protein component in the nucleoprotein. IAA and GA diminish the binding capacity of histones and residual nucleoproteins to DNA at different concentrations.Nucleoproteins containing histones and residual nuclear proteins (DNA/resid. prot. 1:0,5: 0,5) exhibited different thermal stability depending on whether part of the histones or residual nuclear proteins were first bound to DNA. Furthermore, these nucleoproteins showed different thermal stability after treatment with growth substances.     

Glycol methacrylate embedding in enzyme histochemistry: Application to arthropode tissue incubated for demonstration of unspecific esterase and succinic dehydrogenase activity

Summary The final products of unspecific esterase and succinic dehydrogenase were demonstrated in 1–2 m sections of tick salivary glands embedded in glycol methacrylate (GMA). In the esterase experiments, the tissue specimens were incubated after fixation in glutaraldehyde or acroleïn, and then embedded in GMA. For demonstration of succinic dehydrogenase activity, the specimens were incubated prior to glutaraldehyde fixation followed by embedding in GMA. In sections of all preparations intense enzymatic reaction was observed. High resolution light microscopy could efficiently be used for precise locating of the enzymic products, due to excellent morphologic reference in semithin GMA sections.Supported by the Deutsche Forschungsgemeinschaft. Presented in part at the 4th International Congress on Protozoology, Clermont-Ferrand (France), 2.–9. September 1973.The author was fellow of the Deutsche Forschungsgemeinschaft at the Department of Anatomy, Medical School Hannover, Federal Republic of Germany, during part of this study.     

Gesamtbestand an organischen Substanzen der Spinne Tegenaria atrica im Vergleich zu Protophormia terrae novae (Diptera) und Orconectes limosus (Crustacea,Decapoda)

Zusammenfassung Die Pulsationen der Lymphherzen von Normaltieren von Triturus vulgaris L. und T. alpestris Laur. sind unregelmäßig und verändern sich bei Erregung der Tiere. Die Lymphherzfrequenzen sind temperaturabhängig und folgen der R-G-T-Regel. Der Q ₁₀ beträgt bei T. vulgaris 2,5, bei T. alpestris 2,1. In Narkose oder bei Spinaltieren sinkt die Lymphherzfrequenz gegenüber der von Normaltieren ab, der Rhythmus wird regelmäßig. Bei Spinaltieren tritt homolaterale Synchronie auf. Jedes Lymphherz hat ein eigenes motorisches Zentrum im Rückenmark; die Impulse werden über Spinalnerven geleitet. Die Ergebnisse werden mit den von Anuren bekannten verglichen.

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Physiological investigations on the lymph hearts of urodelans

Summary The heart beats of normal individuals of Triturus vulgaris L. and T. alpestris Laur. are irregular and can be altered by excitation of the animal. The frequencies vary with alterations in temperature according to the rule of van t'Hoff. The Q ₁₀ was measured as 2.5 for T. vulgaris and 2.1 for T. alpestris. In anesthetized and in spinal animals the frequencies are strongly reduced and the pulsations become regular. Spinal animals show homolateral synchrony of the lymph heart beats. The motor centres, separated for each lymph heart, are situated in the spinal cord; the impulses are mediated by spinal nerves. The results are compared with those of the Anurans.

     

Bildung Zusätzlicher DNS nach Blockierung der Zellteilung von Tetrahymena durch Actinomycin

Summary The effect of 0,4 g of actinomycin per ml medium on DNA synthesis in synchronous cultures of Tetrahymena pyriformis strain HSM was studied. Synchronous cultures were obtained by selecting cells from a stock culture which were all in the same division phase In this concentration actinomycin inhibits cell division but permits the normal doubling of DNA and furthermore another period of macronuclear DNA synthesis. In this additional DNA production phase the rate and the synchrony of DNA synthesis is reduced as revealed by autoradiography. The production of additional DNA was demonstrated by photometric determination of Feulgen stainable material. These findings indicate that the onset of DNA synthesis is independent of a preceding cell division, of a preceding nuclear division, of the average amount of DNA present, and of the main portion of RNA synthesis.

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Herrn Professor Dr. R. Danneel zu seinem 65. Geburtstag.

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Unterstützt durch Sachbeihilfen der Deutschen Forschungsgemeinschaft.     

Two substrate sites in the renal Na+-d-glucose cotransporter studied by model analysis of phlorizin binding and-d-glucose transport measurements

Summary Time courses of phlorizin binding to the outside of membrane vesicles from porcine renal outer cortex and outer medulla were measured and the obtained families of binding curves were fitted to different binding models. To fit the experimental data a model with two binding sites was required. Optimal fits were obtained if a ratio of low and high affinity phlorizin binding sites of 1:1 was assumed. Na⁺ increased the affinity of both binding sites. By an inside-negative membrane potential the affinity of the high affinity binding site (measured in the presence of 3 mM Na⁺) and of the low affinity binding site (measured in the presence of 3 or 90 mM Na⁺) was increased. Optimal fits were obtained when the rate constants of dissociation were not changed by the membrane potential. In the presence of 90 mM Na⁺ on both membrane sides and with a clamped membrane potential,K _D values of 0.4 and 7.9 M were calculated for the low and high affinity phlorizin binding sites which were observed in outer cortex and in outer medulla. Apparent low and high affinity transport sites were detected by measuring the substrate dependence ofd-glucose uptake in membrane vesicles from outer cortex and outer medulla which is stimulated by an initial gradient of 90 mM Na⁺(out>in). Low and high affinity transport could be fitted with identicalK _m values in outer cortex and outer medulla. An inside-negative membrane potential decreased the apparentK _m ofhigh affinity transport whereas the apparentK _m of low affinity transport was not changed. The data show that in outer cortex and outer medulla of pighigh and low affinity Na⁺-d-glucose cotransporters are present which containlow and high affinity phlorizin binding sites, respectively. It has to be elucidated from future experiments whether equal amounts of low and high affinity transporters are expressed in both kidney regions or whether the low and high affinity transporter are parts of the same glucose transport moleculc.     

Multiple proteins bind to the P2 promoter region of the zein gene pMS1 of maize

Summary A 216 by promoter fragment of the 19 kDa protein zein gene pMS1, containing the CCAAT and TATA boxes, was analysed by a variety of techniques for in vitro interactions with nuclear proteins from endosperm tissue. HMG proteins were found to form stable complexes with these A/T-rich promoter sequences and several specific DNA-binding proteins appear to be involved in the formation of DNA-protein complexes with this fragment. A 29 bp region spanning the two CCAAT boxes was protected from DNase I digestion in footprinting experiments.     

A simple method for mapping aquatic macrophytes

Aerial photography with a balloon-suspended camera is a suitable tool for surveying aquatic vegetation and for measuring water movements. Examples from the lake Lunzer Untersee (Austria) are given.     

Genetic analysis of two tomato mutants affected in the regulation of iron metabolism

Iron is one of the most important micronutrients for plants. Like other organisms, plants have developed active mechanisms for the acquisition of sufficient iron from the soil. Nevertheless, very little is known about the genetic mechanisms that control the active uptake. In tomato, two spontaneously derived mutants are available, which are defective in key steps that control this process. The recessive mutationchloronerva (chln) affects a gene which controls the synthesis of the non-protein amino acid nicotianamine (NA), a key component in the iron physiology of plants. The root system of the recessive mutantfer is unable to induce any of the characteristic responses to iron deficiency and iron uptake is thus completely blocked. We present a characterization of the double mutant, showing that thefer gene is epistatic over thechln gene and thus very likely to be one of the major genetic elements controlling iron physiology in tomato. In order to gain access to these two genes at the molecular level, both mutants were precisely mapped onto the high density RFLP map of tomato. Thechln gene is located on chromosome 1 and thefer gene is on chromosome 6 of tomato. Using this high-resolution map, a chromosome walk has been started to isolate thefer gene by map-based cloning. The isolation of thefer gene will provide new insights into the molecular mechanisms of iron uptake control in plants.