Structure of Leu5-enkephalin bound to a model membrane as determined by high-resolution NMR

Summary Opioid peptides are thought to interact with the cell membrane in their biological journey to the membrane-bound receptor. Both organic solvents and model membranes have been used previously to determine the stable solution conformations of peptide hormones. Leucine enkephalin has been studied in a number of different environments, but with limited resolution. Here it is shown that leucine enkephalin forms a stable type IV -turn structure in dodecylphosphocholine micelles. We have observed a highly solvent-shielded amide proton with no evidence for a complementary hydrogen bond acceptor. The structural details of the peptide as determined by NMR spectroscopy in solution are described.     

Continuous culture of bacteria with biomass retention

Bacterial cells have three phases of growth which are characterized respectively by: (1) balanced growth with a high yield of biomass; (2) balanced growth with lower biomass yield; and (3) unbalanced growth with lowest biomass yield. Phases 2 and 3 are associated with elevated concentrations of the regulatory nucleotides centered on guanosine-5′-diphosphate-3′-diphosphate. Maintenance of the correct growth phase is important in optimizing industrial product formation by bacterial populations.     

Synthesis and bioassay of isoprenoid 3-alkylthio-1,1,1-trifluoro-2-propanones: Potent,selective inhibitors of juvenile hormone esterase

Four 3-alkylthio-1,1,1-trifluoro-2-propanones with juvenile hormone-like side chains were prepared from citronellol and homogeraniol. These substrates were designed as possible transition-state analogs for the juvenile hormone (JH)-specific esterases present in insects. These four isoprenoid trifluoromethyl ketones were assayed in vitro with JH esterase and general esterases from larvae of the cabbage looper, Trichoplusia ni (Lepidoptera, Noctuidae), and with eel acetylcholinesterase and bovine chymotrypsin. JH esterase inhibition I₅₀ values were in the nanomolar range for all four compounds, while the other esterases had I₅₀'S which were 10³ to 10⁵ higher. The high selectivity of these inhibitors is believed to be due to their similarity in size and functionality to natural JH III. Treatment of T. ni larvae in vivo with solutions of the most active analog, 3-[(E)-4,8-dimethyl-3,7-nonadienylthio]-1,1,1-trifluoro-2-propanone (DNTFP) causes a dose-dependent delay in pupation and a concurrent selective inhibition of JH esterase. These data support the hypothesis that the reduction in in vivo JH titer in larval T. ni is due, in part, to hydrolysis of the hormone by selective esterases. DNTFP appears to be competing with JH for the active site of JH esterase.     

Turnover and transport of quinolizidine alkaloids. Diurnal fluctuations of lupanine in the phloem sap,leaves and fruits of Lupinus albus L.

Quinolizidine alkaloids formed in the leaves of Lupinus albus L. are translocated via the phloem to the other plant organs, especially the maturing fruits. Compared with amino-acid transport in the phloem, the alkaloids contribute about 8% to the overall nitrogen being exported from the leaf. Since it is likely that the alkaloids are subsequently degraded in the target tissues a minor role of quinolizidine alkaloids might be nitrogen transport. A marked diurnal fluctuation of alkaloids was observed in the leaves, the phloem sap, the roots and the fruits with an increase during the day and an amplitude of several hundred percent thus providing evidence for a rapid turnover of endogenous alkaloids.Abbreviations QA quinolizidine alkaloids - GLC gas-liquid chromatography     

Multiple redundant circadian oscillators within the isolated avian pineal gland

Summary The avian pineal gland contains a circadian pacemaker that oscillates in vitro. Using a flow-through culture system it is possible to measure melatonin production from very small subsections of an individual gland. We have used this technique to attempt to localize the oscillators in the pineal. Progressive tissue reduction did not affect the rhythmicity of cultured pineals. Multiple pieces (up to eight) from a single pineal all were capable of circadian oscillation — establishing directly that a pineal gland contains at least eight oscillators. All pineal pieces were responsive to light, and single light pulses shifted the phase of the melatonin rhythm. Because pieces equivalent to less than one per cent of the whole gland were rhythmic and because the capacity for oscillation was distributed throughout the gland, an individual pineal appears to be composed of a population of circadian oscillators.     

Successful cardiac allografts in syngeneic radiation chimeras

Summary Successful cardiac allografts were accomplished across the major histocompatibility complex of rats. LEW and F344 (Ag-B ²) rats were lethally irradiated and grafted with WF (Ag-B ¹) hearts on day 0. Either on day 0 or day 2, the hosts were repopulated with syngeneic hemopoietic cells. The best results were obtained (86%) when a mixture of 3.0 × 10⁷ non-adherent syngeneic bone marrow and thymus cells were used to repopulate the recipients. In contrast, all of the WF to LEW heart grafts were rejected within 30 days if syngeneic thoracic duct and bone marrow cells were used to repopulate the host.Supported by Grant HL18186 from the National Institutes of HealthRecipient of a Research Career Development Award CA70879 from the National Institutes of Health     

Die Beinmuskulatur und ihre Innervation bei der VogelspinneDugesiella hentzi (Ch.) (Araneae,Aviculariidae)

Zusammenfassung Gestützt auf präparative Untersuchungen und histologische Serienschnitte werden Zahl, Lage, Funktion und nervöse Versorgung aller Muskeln in den Laufbeinen der erwachsenen VogelspinneDugesiella hentzi (Ch.) beschrieben. In den acht Laufbeinen können gleichermaßen jeweils dreißig Muskeln unterschieden werden.Bis auf eine Ausnahme (M. 30) erfolgt die Innervation sämtlicher Beinmuskeln durch den Beinnerv B, wobei die Versorgung durch mehrere (bis zu 6) Nervenäste pro Muskel die Regel ist. Jeder Ast aus Nerv B enthält eine große Anzahl von Axonen. Die aus Ansatz und Ursprung ersichtliche gemeinsame Funktion verschiedener Beinmuskeln spiegelt sich auch in der Innervation aus gemeinsamen Seitenästen von Nerv B wieder.Soweit möglich werden die vermutlich homologen Beinmuskeln aus Untersuchungen anderer Autoren an anderen Arten gegenübergestellt.

---

Anatomy of the leg muscles and their innervation in the tarantulaDugesiella hentzi (Ch.) (Araneae, Aviculariidae)

Summary All muscles in the walking legs of the adult tarantulaDugesiella hentzi (Ch.) are described according to their position, function, and innervation pattern. Each leg contains 30 muscles. With the exception of one (M. 30) all of them receive their motor innervation through multiple branches from the main motor nerve B. Muscle 30 is innervated through the mixed nerve A. Each branch leaving nerve B contains a large number of axons.Similarities in the function of different muscles as derived from their attachment at particular leg joints are reflected in the innervation pattern by common branches of nerve B.The leg muscles fromDugesiella are homologized with those of six other species of spiders from different families.

     

Responsiveness of the lamb ductus arteriosus to prostaglandins and their metabolites

The relative potencies of the prostaglandins A₁, A₂, E₁, E₂, F_2α and their 15-keto-, 15-keto-13,14-dihydro-, and 13,14-dihydro-metabolites were investigated on isolated lamb ductus arteriosus preparations contracted by exposure to elevated PO₂. All the prostaglandins (except PGF_2α and its 15-keto-metabolites) relaxed the tissue. However, only PGE₁, E₂, and their 13,14-dihydro-metabolites, were effective at concentrations below 10⁻⁸ M. Therefore, events that alter metabolism of circulating PGs in the perinatal period may have significant effects on the relative patency or closure of the ductus arteriosus.