Einfluß der Konzentration der Zuckerlösung auf den Gesang und das Balzverhalten des Gelbbauchnektarvogels (Nectarinia venusta)*

Different concentrations of a sucrose solution vary the courtship song and behaviour of the male yellow-bellied sunbird Nectarinia venusta- the duration of subsong, total singing duration, and the absolute number of full song phrases. With high concentrations the sunbird sings more full song phrases but less subsong during the courtship season than otherwise. The various effects are described.     

Inhibitory effect of irradiation products of cyclic adenosine-monophosphate on the relaxing ability of smooth muscle preparations

Summary In a previous publication it has been shown that the radiation induced physiological inactivation of dibutyryl-cAMP was far more pronounced than the chemical modification (Schachinger et al. 1981). In this paper it will be shown, that irradiation of dib-cAMP in solution resulted in the formation of monobutyryl cAMP and other not yet completely identified hydroxylated derivatives as well as a decomposition of the purine structure. Moreover, irradiated dib-cAMP inhibited the physiological activity of not irradiated dib-cAMP on the smooth muscle. From the data an effectiveK _m -value for dib-cAMP of 2.4 × 10^–5 M was determined and an effectiveK _I -value of 1.3 × 10^–6 M was found for the irradiation products, i.e., a tenfold affinity of the latter compared to unirradiated dib-cAMP. The results are discussed with respect to a better understanding of dose-response curves for chemical and physiological inactivation.     

Characterization of the proteins of isolated human platelet alpha-granules. Evidence for a separate alpha-granule-pool of the glycoproteins IIb and IIIa

The protein composition of a well-defined alpha-granule preparation isolated from human platelets has been studied. Crossed immunoelectrophoresis against polyspecific platelet antibodies revealed more than 20 immunoprecipitates. The glycoprotein IIb-IIIa complex represented a major antigen in the Triton X-100-solubilized alpha-granule preparation and cross-reacted with the corresponding platelet membrane antigen. Furthermore, after lactoperoxidase-catalyzed 125I-iodination of whole platelets it was not labelled, in contrast to its membrane-located counterpart. This indicates an intracellular location of glycoproteins IIb and IIIa, probably as constituents of the alpha-granules. Fibrinogen, platelet factor 4, albumin, factor VIII-related antigen and the main granule glycoprotein (thrombinsensitive protein, thrombospondin) were identified in the alpha-granule preparation by the crossed immunoelectrophoresis technique. Crossed affinity immunoelectrophoresis using lectins revealed the presence of at least seven glycoproteins, and six sialoglycoproteins were identified by their altered electrophoretic mobility after neuraminidase treatment. Sodium dodecyl sulphate polyacrylamide gel electrophoresis of reduced samples of the alpha-granules revealed at least 15 Coomassie Brilliant Blue-staining polypeptide bands, one of which comigrated with myosin heavy chain. No prominent band was observed in the actin region. Five glycopolypeptide bands were observed after periodic acid-Schiff staining. The dominant three represented the main granule glycoprotein, glycoprotein IIb and glycoprotein IIIa, respectively. More glycoproteins seem to be present in the alpha-granules than was previously recognized.     

Properties of an endonuclease activity in Micrococcus luteus acting on gamma-irradiated DNA and on apurinic DNA

A protein fraction from Micrococcus luteus with endonuclease activity against gamma-irradiated DNA was isolated and characterized. An additional activity on apurinic sites could not be separated, either by sucrose gradient sedimentation or by gel filtration through Sephadex G 100. From gel filtration, a molecular weight of about 25 000 was calculated for both endonuclease activities. The endonuclease activity against gamma-irradiated DNA was stimulated five-fold with 5 mM Mg++, whereas that against apurinic sites was less dependent on the Mg++ concentration. 100 mM KCl inhibited the gamma-ray endonuclease, but not the apurinic endonuclease activity. In gamma-irradiated RNA the protein recognized 1.65 endonuclease sensitive sites per radiation induced single-strand break, among which are 0.45 alkali labile lesions in the nucleotide strand. The affinity of the enzyme for the endonuclease sensitive site was evaluated resulting in a Km-value of 73 nM.     

Lactose carrier protein of Escherichia coli. Structure and expression of plasmids carrying the Y gene of the lac operon

The previously described hybrid plasmid pC7 which carries lacI+O+delta(Z)Y+A+ on a 12.3 X 10(6)-Mr DNA fragment [Teather et al. (1978) Mol. Gen. Genet. 159, 239-248] was partially digested with the restriction endonuclease EcoRI under conditions reducing the recognition sequence to d(A-A-T-T) and ligated to the vector pB322. lac Y-carrying inserts of various sized (Mr 1.5-4.7 X 10(6)) were obtained. Hybrid plasmid pTE18 (2300-base-pair insert) carries part of the I (repressor) gene, the promotor-operator region, part of the Z (beta-galactosidase) gene, the Y (lactose carrier) gene and part of the A (transacetylase) gene. Upon induction of pTE18-harbouring strains the Y-gene product is expressed at a nearly constant rate for several generations and accumulates to a level of 12-16% of the total cytoplasmic membrane protein. Integration into the membrane leads to active carrier as judged by binding and transport measurements.     

Investigations on the lectin-producing cells in the sponge Axinella polypoides (Schmidt)

Summary The localization of two carbohydrate binding proteins, so-called lectins, was studied in the sponge tissue of Axinella polypoides by light and immunofluorescence microscopy. They do not occur at the cellular surface of any cell type, but they are stored in vesicles of the spherulous cells. After short formaldehyde fixation spherulous cells can be isolated and they release the active lectins upon lysis in distilled water.Electron microscopical studies of spherulous cells show that they contain almost nothing else but a small nucleus and vesicles of different size and number. Small vesicles are full of an electron dense material, whereas the content of large vesicles has a fluffy and fibrillar structure. Spherulous cells are large and tightly packed in the outer layer of the ectosome and in the mesh work of the spongin fibres of the central axis. They are small and scattered in the inner layer of the ectosome, and they are found throughout the choanosome. The function of the lectins is not clearly defined, and different alternatives such as participation in glycoprotein synthesis, immunological defense, or carbohydrate transport are possible.This study was supported by a grant from the Deutsche ForschungsgemeinschaftWe are gratefully indebted to Dr. D. Keyser for his help in our electron microscopical studies     

Preliminary studies of plasma growth hormone releasing activity during medical therapy of acromegaly.

The in vitro growth hormone releasing activity of plasma obtained from six acromegalic subjects was measured before and during therapy. In five subjects, plasmas were obtained before and during successful medical therapy with medroxyprogesterone acetate (MPA). The sixth subject was sampled before and after transphenoidal Sr90-induced hypopituitarism. All subjects had a decrement in fasting growth hormone levels with respective therapies (29-88%). The in vitro growth hormone released from Rhesus monkey anterior pituitaries was assessed after incubating one lateral half in control plasma (pre-therapy) and the contralateral pituitary half in plasma obtained during or after therapy. Studies with plasmas obtained from the five patients successfully treated with MPA showed a decreased in growth hormone releasing activity during therapy in all (18-57%). Plasma obtained after Sr90 pituitary ablation in the sixth subject had 35% more growth hormone releasing activity than obtained before therapy. These results suggest that active acromegalics who respond to MPA with significantly lowered growth hormone levels may actually achieve this response because of a decrease in growth hormone releasing factor measured peripherally. The opposite response in one acromegalic subject, following Sr90 pituitary ablation and hypopituitarism, suggests that growth hormone releasing factor secretion may increase when growth hormone levels are lowered by ablative therapy.     

Analysis of gene function of bacteriophage phi 29 of Bacillus subtilis: identification of cistrons essential for viral assembly.

Restrictive infection of Bacillus subtilis by suppressor-sensitive (sus) mutants of phi 29 has been used to search for cistrons that function in viral assembly. The products of cistrons 7, 9, 10, and 16 are necessary for head morphogenesis. The neck upper collar protein P10 and the tail protein P9 must be present for DNA packaging to occur. The protein P7 must be present for phage-related particles to form. A prohead-like particle has been isolated during 16-restrictive infection. The particle is composed of the proteins Hd, P10, F, and P7. P16 must function for DNA-filled particles to accumulate. A DNA-containing particle produced in the absence of the cistron 11 product may be an intermediate in the phi 29 assembly pathway. The protein P13 interacts with P9 and P11 to form a stable DNA-filled particle. The products of cistrons 2 and 3 are essential for viral DNA synthesis, and in their absence virus-related particles are not detected.