Urine selenium level in healthy adult population

The level of urine selenium in healthy adult population, 230 persons, was examined. Persons were selected regarding sex, ages, and smoking habits. No differences versus these observations have been found. For a total, group values are 16.96 Se nmol/creatinine mmol, SD=5.44. It is possible from a single-void specimen to express daily excretion of selenium.     

Progress since the first international symposium: ‘Genetic aspects of plant mineral nutrition’, Beograd, 1982, and perspectives of future research

Summary The paper discusses the problems of genetic aspects of plant mineral nutrition in the light of the results presented at the First and Second Symposia on ‘Genetic Aspects of Plant Mineral Nutrition’ organized in Beograd in 1982 and Madison in 1985, respectively. On the basis of the results, future directions of research are discussed. The papers deal with the concentration and content of mineral nutrients in different genotypes, physiological and biochemical aspects of the genetic specificity of plant mineral nutrition, relations between plant genotypes and nitrogen fixing micro-organism strains, as well as with some related problems which have been investigated to a lesser extent. Particular attention is paid to papers and problems referring to genetic and breeding research work linked with genetic aspects of plant mineral nutrition as well as the possibilities of developing new cultivars requiring certain soil and mineral nutrition conditions for their cultivation.     

Rec dependence of mu transposition from P22-transduced fragments.

Derivatives of bacteriophage Mu carrying a lac operon and a selectable drug resistance element (Mu d phages) are frequently used tools of bacterial genetics. Mu d prophages used in this way can be treated as transposons, in that the inserted material can be transduced from one strain to another by general transducing phages, such as P1 and P22. When a Mu d prophage is transduced into a new recipient by P1 or P22, the Mu d element can transpose from the transduced fragment into the bacterial chromosome. Transposition of the Mu d element from a P22-transduced fragment shows several striking differences from transposition of a Mu d genome injected by a Mu virion. First, the frequency of transposition from a transduced fragment is greatly enhanced by a P22 helper genome. Second, transposition requires the host recA, B, and C functions. Transposition of Mu following injection by a Mu virion is rec independent. While the basis of these observations is not understood, we suggest that the Mu X protein, a 65-kilodalton protein injected by a Mu virion and required for Mu transposition, may not be packaged by P22. We suggest that the effects seen reflect the behavior of a Mu genome in the absence of the X protein.     

Neuronal calcium channel antagonists. Discrimination between calcium channel subtypes using omega-conotoxin from Conus magus venom

The omega-conotoxins from the venom of fish-hunting cone snails are probably the most useful of presently available ligands for neuronal Ca channels from vertebrates. Two of these peptide toxins, omega-conotoxins MVIIA and MVIIB from the venom of Conus magus, were purified. The amino acid sequences show significant differences from omega-conotoxins from Conus geographus. Total synthesis of omega-conotoxin MVIIA was achieved, and biologically active radiolabeled toxin was produced by iodination. Although omega-conotoxins from C. geographus (GVIA) and C. magus (MVIIA) appear to compete for the same sites in mammalian brain, in amphibian brain the high-affinity binding of omega-conotoxin MVIIA has narrower specificity. In this system, it is demonstrated that a combination of two omega-conotoxins can be used for biochemically defining receptor subtypes and suggested that these correspond to subtypes of neuronal Ca2+ channels.     

DNA ligase and the pyridine nucleotide cycle in Salmonella typhimurium.

Bacterial DNA ligases use NAD as an energy source. In this study we addressed two questions about these enzymes. First, what is the physiological consequence of completely removing the NAD-dependent enzyme and replacing it with an ATP-dependent DNA ligase? We constructed Salmonella typhimurium strains in which the endogenous NAD-dependent DNA ligase activity was inactivated by an insertion mutation and the ATP-dependent enzyme from bacteriophage T4 was provided by a cloned phage gene. Such strains were physiologically indistinguishable from the wild type, even under conditions of UV irradiation or treatment with alkylating agents. These results suggest that specific functional interactions between DNA ligase and other replication and repair enzymes may be unimportant under the conditions tested. Second, the importance of DNA ligation as the initiating event of the bacterial pyridine nucleotide cycle was critically assessed in these mutant strains. Surprisingly, our results indicate that DNA ligation makes a minimal contribution to the pyridine nucleotide cycle; the Salmonella strains with only an ATP-dependent ligase had the same NAD turnover rates as the wild-type strain with an NAD-dependent ligase. However, we found that NAD turnover was significantly decreased under anaerobic conditions. We suggest that most intracellular pyridine nucleotide breakdown occurs in a process that protects the cell against oxygen damage but involves a biochemical mechanism other than DNA ligation.     

Zur Morphologie und Systematik desTrebouxia-Phycobionten im Thallus vonUsnea longissima (Lecanorales)

In the lichen genusUsnea different species ofTrebouxia-phycobionts as well as different haustorial types are known. The isolated and cultivated phycobiont ofUsnea longissima Ach. was studied by light- and electron microscopy and resembles in cytomorphological details the type ofTrebouxia impressa Ahmad. In addition to simple wall-to-wall contacts between the symbiotic components also intraparietal (=intrawall-)haustoria could be observed as the normal interaction type.

Frau Prof. Dr.Elisabeth Tschermak-Woess zu ihrem 70. Geburtstag gewidmet.     

The temporal region and the supramastoid ridge in mesolithic skulls from Padina in the Iron Gate Gorge of the Danube

Studies of the morphological features of the temporal region of mesolithic skulls from Padina in the Iron Gate Gorge of the Danube revealed a very prominent and large supramastoid ridge which is the most striking feature in skulls of both sexes. Mastoid processes were larger in male skulls, but in 25% of the cases there was an overlap between the size of the processes in male and female specimens. The mastoid ridge was prominent in both sexes. The digastric fossa was always well defined in both sexes and in the two thirds of the skull specimens it was deep. The posterior root of the zygoma was prominent in all the skulls, but it was better developed in the male specimens. The parietotemporal suture in both sexes rises above the level of the pterion. There were no morphological or anthropometrical differences between the left and the right side of individual skulls outside the limits of natural asymmetry. All these morphological characteristics of the temporal region may help in racial and sexual diagnosis of the Mesolithic skulls from the Iron Gate Gorge.     

Electric organ polyamines and their effects on the acetylcholine receptor

1. The electric organ of Torpedo nobiliana contained putrescine (PUT), spermidine (SPD), spermine (SPM), and cadaverine (CAD). Traces of acetylated SPD and SPM were occasionaly seen. 2. Upon fractionation of the tissue by differential centrifugation, the polyamines (PA) were found predominantly in the soluble fraction. The postsynaptic membrane fraction, containing a high concentration of acetylcholine receptor (AChR), was proportionally enriched in SPM. The molar ratio of SPM to AChR was approximately two in these membranes. 3. The effect of exogeneous PA on AChR function was studied by two methods: carbamoylcholine (CCh)-dependent 86Rb+ influx into receptor-rich membrane vesicles and [alpha-125I]bungarotoxin (Bgt) binding to the AChR. 4. SPM inhibited both ion influx and the rate of Bgt binding at concentrations above 1 mM, and therefore it appears to act as a competitive antagonist of the AChR. 5. At submicromolar concentrations, and only after preincubation with the receptor-rich membrane, SPM and PUT increased the ion influx by about 20% over control values. 6. Preincubation with 100 nM SPM did not affect the equilibrium binding of iodinated toxin or the rate of toxin binding, and therefore SPM was not uncovering new receptors. 7. By measuring the initial rate of toxin binding after different periods of preincubation with 1 microM CCh, the rate of the slow phase of receptor desensitization was determined. This rate was not changed by 100 nM SPM. 8. Although these results suggest that at low concentrations SPM is a positive modulator of the AChR, the precise mechanism of action is not determined yet.