Dynamics of a hydrophobic peptide in membrane bilayers by solid-state nuclear magnetic resonance

Solid-state NMR studies of the dynamics of a synthetic hydrophobic peptide, tert-butyloxycarbonylleucylphenylalanine methyl ester (Boc-Leu-Phe-OMe), in phospholipid bilayers are described. Motionally averaged powder pattern line shapes from 2H- and 15N-labeled backbone and side-chain sites of the peptide in phospholipid bilayers demonstrate the presence of both overall and internal reorientations of substantial amplitude. The peptide motions are shown to be strongly influenced by the motions of the lipids.     

Initial stages in the course of adventitious bud formation on embryos of Picea abies

Adventitious buds on embryos of Picea abies (L.) Karst. developed after a pulse treatment with 250 μ M benzyladenine (BA) of pH 5.5 for 2 h. Light and temperature regimes were not critical during the initial stages. Adventitious buds developed faster after a pulse treatment and the variation among different experiments was lower compared to when the embryos were cultured on media supplemented with BA. Various stages of the differentiation of adventitious buds were identified: stage 1 - appearance of meristematic centres (approximately the first two weeks); stage 2 - development of adventitious bud primordia (approximately the third week); stage 3 - adventitious bud development (from approximately the 4th to the 8th week). This system may be used for further studies on bud differentiation.     

Transient enhancement of serum somatomedin levels prior to weaning of growth-impaired vasopressin-deficient Brattleboro rats

Somatomedin serum levels of congenitally vasopressin-deficient Brattleboro rats were determined postnatally between day 1 and 55, and compared with heterozygous control values. Assays were performed with a radioimmunoassay of insulin-like growth factor 1 (IGF-1). A transient enhancement of immunoreactive IGF-1 levels between day 8 and 21 of age and a reduction in adulthood was found. This observation shows that the early growth impairments of the Brattleboro mutant are not due to a deficiency of IGF-1.     

Radiosensitization, pharmacokinetics, and toxicity of a 2-nitroimidazole nucleoside (RA-263)

A 2-nitroimidazole nucleoside, 1-(2',3'-dideoxy-alpha-D-erythro-hex-2'-enopyranosyl)-2-nitroimida zole (RA-263), has been investigated for its radiosensitization, pharmacokinetics, and toxicity properties. The in vitro radiosensitization tests against hypoxic Chinese hamster (V-79) cells demonstrated that RA-263 was a more potent radiosensitizer than misonidazole and at 2 mM concentration approached the oxic curve. Significant in vitro radiosensitization activity was also observed in EMT6 mammary tumor cells. The in vitro cytotoxicity data suggested that RA-263 is considerably more toxic to hypoxic cells than misonidazole. The increased cytotoxicity may be related to its higher depletion of nonprotein thiols (NPSH) than misonidazole. The combined effects of radiosensitization and hypoxic cell toxicity were measured by preincubation of the V-79 cells for 4 h under hypoxic conditions before irradiation. The results demonstrated a synergistic response by causing a significant decrease in the extrapolation number with loss of shoulder of the radiation survival curves. The in vivo radiosensitization experiments conducted by the in vivo-in vitro cloning assay with the EMT6 mammary tumor indicate that RA-263 is an effective sensitizer. Pharmacokinetic data suggested that RA-263 was eliminated from plasma by a rapid alpha phase and a slower beta phase with T 1/2 of 36 and 72 min, respectively. The concentration in the brain was approximately one-sixth of tumor concentration, suggesting that RA-263 is excluded from the CNS. Moreover, RA-263 was two times less toxic than misonidazole on equimolar basis by acute LD50 tests. This agent was also significantly less mutagenic than misonidazole in a strain of Escherichia coli.     

Antibodies to spiroperidol and their anti-idiotypes as probes for studying dopamine receptors

Spiroperidol was covalently conjugated to bovine serum albumin (BSA). Conjugated spiroperidol was almost as efficient as free spiroperidol in its binding capacity to dopamine receptor. Antibodies to spiroperidol were produced in rabbits following repeated immunizations with the conjugate of spiroperidol and BSA. The obtained antibodies have an apparent K_D of 0.02 nM for [³H]-spiroperidol. These antibodies bind also to other butyrophenones with IC₅₀ values three to four orders of magnitude higher than the IC₅₀ obtained with unlabeled spiroperidol. Antibodies were purified from anti-spiroperidol sera by affinity chromatography. Anti-idiotypic antibodies were raised in rabbits by immunization with the purified anti-spiroperidol antibodies. Some rabbits produced anti-idiotypic antibodies which bind to rat and calf striatum.     

Monoclonal antibodies modify acetylcholine-induced ionic channel properties in cultured chick myoballs

Summary Monoclonal antibodies directed against the cholinergic binding site of the acetylcholine receptor were found to alter the ion channel properties in cultured chick myoballs. Time and dose dependent reduction in acetylcholine sensitivity was observed. Noise analysis experiments indicated a decrease in the mean single channel conductance and an increase in the mean single channel open time.     

The effect of osmotic `shock'' on the swelling pattern and respiratory control of rat-liver mitochondria

1. Rat-liver mitochondria suspended in 0.25m-sucrose were exposed for a few seconds to strongly hypo-osmotic conditions, and then the osmolarity of the medium was raised again to 0.25 with the aid of tris chloride (osmotic ;shock'). 2. Mitochondria after hypo-osmotic pretreatment lost their capacity for slow energy-dependent swelling in iso-osmotic tris buffer and showed no respiratory control. 3. Swelling could be induced in the ;shocked' mitochondria by ATP but not by addition of respiratory substrates. 4. It was shown that cytochrome c is lost from ;shocked' mitochondria when they come into contact with the tris buffer present in the assay medium, and that the changes observed in the pattern of swelling, as well as in respiratory control, are directly connected with this loss of cytochrome c. 5. The results of the investigation are discussed with regard to the role of cytochrome c in swelling and respiratory control.     

Differential Effect of Polyamines on T4 Morphogenesis

The 5-fluorouracil (5 FU) technique for the phenotypic reversion of amber mutants was used to demonstrate that under certain circumstances, in the presence of putrescine or spermidine, early mutants have an enhanced response to 5 FU, whereas late mutants have a delayed response. Bacteria infected by T4D wild-type bacteriophage did not produce phage in the presence of high putrescine concentrations. Pulse treatments with putrescine showed that the production of lysozyme depends on a putrescine-sensitive process that begins immediately after infection at 26 C and ends at 36 min or even later. The addition of putrescine at any time during the critical period between 0 and 36 min led to a corresponding delay in lysozyme synthesis after the inhibitor was removed. Intracellular phage maturation was delayed by the addition of 100 mumoles of putrescine per ml. Early enzymes were not affected by the diamine, but the level of phage deoxyribonucleic acid was considerably decreased by the inhibitor. The putrescine-sensitive process that affects the timing of maturation is suggested to be the natural process controlling the T4 "clock."     

Relation between optical configuration and immunogenicity of synthetic polypeptides

1. Three random linear copolymers composed of two or three of the amino acids d-tyrosine, d-glutamic acid, d-alanine and d-lysine, and a branched multichain copolymer with a poly-d-lysine backbone and polymeric side chains of d-tyrosine and d-glutamic acid, were found to be non-antigenic in rabbits, by precipitin and passive cutaneous anaphylaxis, and in guinea pigs, by delayed hypersensitivity tests. The corresponding four copolymers of l-amino acids were shown to be antigenic by all the three criteria. 2. No immunological cross-reactions were observed between the polypeptides composed of d-amino acids and the corresponding l-amino acid copolymers. 3. Similarly, an azobenzenearsonic acid conjugate of poly-d-tyrosine was shown to be non-antigenic in guinea pigs, in contrast with an analogous conjugate of poly-l-tyrosine. Animals sensitized with the conjugate of poly-l-tyrosine did not exhibit delayed skin reactions, when cross-tested with the d-conjugate. 4. A linear polymer composed of d-tyrosine, l-glutamic acid and l-alanine was found to be immunogenic and to cross-react with the corresponding polymer composed exclusively of d-amino acids.     

Studies of sibling Drosophila species from Laguna Verde, Veracruz, Mexico: I. Species frequencies, viability, desiccation resistance, and vagility

The sibling species Drosophila melanogaster and D. simulans were collected at Laguna Verde, Veracruz, Mexico. D. melanogaster was found in significantly greater frequency than was D. simulans. Ten isofemale lines of each species were tested for egg to adult viability, desiccation resistance, and vagility. D. melanogaster surpassed D. simulans in all three characteristics. The findings are discussed with reference to the climatic conditions at Laguna Verde and the expected effect of such an environment on the relative frequencies of these species. The dichotomous results in regard to desiccation resistance and vagility that were observed between recently collected D. melanogaster and the Oregon-R laboratory stock of that species are also discussed.