RNA biosynthesis in isolated prothoracic glands ofTenebrio molitor in vitro

Summary The prothoracic Glands ofTenebrio molitor synthesize in vitro mainly rRNA. The rate of RNA synthesis reaches a maximum at day 10 of the last larval instar, which coincides with the event of apolysis.The work was supported by the Deutsche Forschungsgemeinschaft. We thank Dr.H. Winter, Heidelberg, for helpful suggestions for the RNA separations.     

Isolation and structure of a novel C-terminally amidated opioid peptide, amidorphin, from bovine adrenal medulla

Biologically active peptide hormones and neurotransmitters have been shown to be enzymatically liberated from larger, inactive precursor molecules by tissue-specific post-translational processing, particularly at the typical cleavage signals of paired basic residues. Subsequent N-terminal or C-terminal modifications may be of importance in regulating the biological activities of these peptides. C-terminal alpha-amidation is considered to be essential for the biological function of several non-opioid peptides. Here we present the isolation and structure of a novel C-terminally amidated opioid peptide, amidorphin, from bovine adrenal medulla. Amidorphin and the recently isolated octapeptide metorphamide (adrenorphin) are the only endogenous opioid peptides in mammals known to possess a C-terminal amide group. The amino acid sequence of amidorphin corresponds to the sequence 104-129 of bovine proenkephalin A. Very high concentrations of amidorphin were detected in bovine adrenal medulla and in a further endocrinological system, the hypothalamic-neurohypophyseal axis. Amidorphin may therefore be considered to be a major gene product of the opioid peptide precursor proenkephalin A in these endocrine tissues.     

Zur Polymorphie eines Chromosoms innerhalb von Populationen des LaufkäfersCarabus auronitens Fabr

Summary C. auronitens has 26 autosomes (2n), from which one pair — calledA-chromosomes — is relatively long.A-chromosomes consist of an euchromatic and a heterochromatic arm. In 63% of the individuals, theA-chromosomes are intraindividually anisomorph with regard to the length of their heterochromatic arm. According to its length, this arm shows 0–3 secondary constrictions. Hence there are at least 4 different forms of theA-chromosome.     

A dynorphinergic pathway of Leu-enkephalin production in rat substantia nigra

The amino acid sequence of the opioid peptide Leu-enkephalin is found within several larger peptides, which are generated from the precursors proenkephalin and prodynorphin. Proenkephalin contains four copies of the sequence of Met-enkephalin, a single copy of the sequence of Leu-enkephalin and one copy each of two extended Met-enkephalin sequences. Proenkephalin contains three peptides--alpha-neo-endorphin, dynorphin A and dynorphin B--the N-terminal sequences of which are identical to that of Leu-enkephalin. There is good evidence that the large amounts of Leu-enkephalin found in the adrenal medulla are generated from the precursor proenkephalin, but as yet prodynorphin has not been shown to be processed to yield Leu-enkephalin. We show here that the relatively high levels of Leu-enkephalin found in the rat substantia nigra are supplied by striatonigral axons and generated from the precursor prodynorphin.     

Electrostatic orientation during electron transfer between flavodoxin and cytochrome c

Various studies have shown that reaction rates between reversibly binding electron transfer proteins depend strongly on solution ionic strength. These observations suggest that intermolecular electrostatic interactions are important in facilitating the formation of a productive reaction complex. A recently examined system involves the reduction of vertebrate cytochrome c by bacterial flavodoxin. Although this is a nonphysiological reaction, it proceeds with rates typical for natural partners and is similarly inhibited at high ionic strengths. Here we describe computational studies which examine the role of electrostatics in the formation of a putative reaction complex between flavodoxin and cytochrome c. The results suggest that electrostatic interactions preorient the molecules before they make physical contact, facilitating the formation of an optimal reaction complex.     

Cocarcinogens of the diterpene ester type fromCroton flavens L. and esophageal cancer in Curaçao

Summary From the roots ofCroton flavens L., 3 highly irritant and tumor promoting Croton factorsF ₁–F ₃ and the corresponding 3 cryptic Croton factorsF₁–F₃ were isolated and characterized as novel esters of 16-hydroxy- and 4-deoxy-16-hydroxyphorbol, respectively. These findings suggest that tumor promoters of the phorbol ester type, ingested through the widespread and frequent use ofCroton flavens according to local habits, may be causally related to the well recognized high rate of esophageal cancer on Curaçao.Dedicated to Prof. Dr H. P. Rusch, Director Wisconsin Clinical Cancer Center, Madison, Wis. USA, on occasion of his 70th birthday. We wish to thank Dr J.F. Morton, Morton Collectanea, University of Miami, Florida, USA, for kindly supplying us with the plant material.     

Influence of phosphorus supply and light intensity on mycorrhizal response inPisum-Rhizobium-Glomus symbiosis

The influence of mycorrhizal colonization withGlomus mosseae on parameters of N₂ fixation and plant growth was studied in pot experiments with pea plants (Pisum sativum L.) infected withRhizobium leguminosarum and supplied with varied levels of phosphorus (P) and nitrogen (N). Reduced light intensities were used to evaluate the dependence of the microsymbionts on assimilate supply. In plants grown with low P supply, mycorrhization increased the concentration of P in shoots, and thus N₂ fixation. Reduced light intensity significantly depressed mycorrhizal colonization and nodule growth in low-P plants. When P supply did not limit plant growth and N₂ fixation, however, the percentage of mycorrhizal colonization was reduced due to the higher P status, and the microsymbionts were not impaired by low light intensities. To maximize carbohydrate supply, another experiment was carried out at high light intensity of 900 mol m^–2s^–1 and with non-limiting P supply. Nitrogen fertilization, given as starter N, enhanced plant growth, but delayed nodule formation. Towards flowering, nodulation rapidly increased, but less so inGlomus inoculated plants. After 28 days mycorrhizal plants were lower in shoot dry weight, nodule dry weight and nitrogenase activity. The results suggest that under many, but not all, environmental conditions the host plant is able to restrict mycorrhizal colonization and, thus, to prevent impairment ofRhizobium symbiosis.deceased in May 1994     

Soluble CD4 blocks the infectivity of diverse strains of HIV and SIV for T cells and monocytes but not for brain and muscle cells

The CD4 antigen has been subverted as a receptor by the human and simian immunodeficiency viruses (HIV-1, HIV-2 and SIV). Several groups have reported that recombinant, soluble forms of the CD4 molecule (sCD4) block the infection of T lymphocytes by HIV-1, as CD4 binds the HIV envelope glycoprotein, gp120, with high affinity. We now report that sCD4 blocks diverse strains of HIV-1, HIV-2 and SIV, but is less effective for HIV-2. The blocking effect is apparent even after adsorption of virions to CD4 cells. Soluble CD4 prevents HIV infection of T-lymphocytic and myelomonocytic cell lines, but neither sCD4 nor anti-CD4 antibodies inhibit infection of glioma and rhabdomyosarcoma cell lines.     

Rationality in the Discovery of Empirical Laws

In this paper I argue against the traditional viewthat in discovery processes there is no place forrational decisions. First I argue that some historicalprocesses in which an empirical law was developed,were rational. Second, I identify some of themethodological rules that we can follow in order to berational when constructing an empirical law. Finally,I argue that people who deny that scientific discoverycan be rational do not understand the nature ofmethodological rules.