Pigment patterns in mutants affecting the biosynthesis of pteridines and xanthommatin in Drosophila melanogaster

Eye-color mutants of Drosophila melanogaster have been analyzed for their pigment content and related metabolites. Xanthommatin and dihydroxanthommatin (pigments causing brown eye color) were measured after selective extraction in acidified butanol. Pteridines (pigments causing red eye color) were quantitated after separation of 28 spots by thin-layer chromatography, most of which are pteridines and a few of which are fluorescent metabolites from the xanthommatin pathway. Pigment patterns have been studied in 45 loci. The pteridine pathway ramifies into two double branches giving rise to isoxanthopterin, drosopterins, and biopterin as final products. The regulatory relationship among the branches and the metabolic blockage of the mutants are discussed. The Hn locus is proposed to regulate pteridine synthesis in a step between pyruvoyltetrahydropterin and dihydropterin. The results also indicate that the synthesis and accumulation of xanthommatin in the eyes might be related to the synthesis of pteridines.Support for this work was provided to J.F. in part by a grant from the Ministerio de Universidades e Investigación (Spain) and to F.J.S. by a grant from the Ministerio de Educación y Ciencia (Spain).     

Identification of host range determinants in the Rhizobium species MPIK3030

Summary R. meliloti primarily nodulates Medicago sativa but cannot nodulate Macroptilium atropurpureum. By introducing an 11.4 kb region into R. meliloti from the Symplasmid of Rhizobium strain MPIK3030, the host range of the R. meliloti transconjugants were shown to be extended to M. atropurpureum, one of the hosts of MPIK3030 but not normally nodulated by R. meliloti. The region responsible for host range extension was isolated by mass conjugating a clone bank from MPIK3030 into the R. meliloti wild type, and subsequent screening for nodulation on M. atropurpureum. Using deleted derivatives of a plasmid reisolated from endosymbiotic bacteria, the host range region was further narrowed down to three EcoRI fragments. Tn5 mutagenesis allowed the isolation of three discrete regions on an 11.4 kb section, which are involved in the extension of host range to M. atropurpureum. Finally, complementation experiments performed with R. meliloti common nod and hsn mutants indicated that none of the genes involved in the early steps of nodulation, including host-range functions, can be complemented by genes carried on the 11.4 kb fragment derived from MPIK3030.     

Primary productivity and related parameters in three different types of inland waters in Sri Lanka

Gross and net primary production together with chlorophyll-a biomass were investigated with respect to depth and diurnal changes in three categories of inland waters (reservoirs, temporary ponds, brackish water lagoons) in Sri Lanka. Ten field sites, in both the dry and wet zones of the island, were investigated. Bimodal productivity profiles were recorded in two of the three reservoirs studied. The diel pattern of net photosynthetic rate varied between sites although peak photosynthetic efficiency occurred at solar noon. Surface photoinhibition was characteristic of the reservoirs and brackish water lagoons but not of the temporary ponds. Mean gross primary production was 3.02 g C m^–2 d^–1 but was higher in the temporary ponds than in the reservoirs. The gross primary production in the brackish water Koggala Lagoon at 0.08 g C m^–2 d^–1 is a record low for tropical lagoons and was 2.5 times less than the two other lagoons investigated. Variability in net primary production between sites was similar to the variation in gross production with a relatively low mean value for tropical inland waters of 0.495 C m^–2 d^–1. Mean maximum photosynthetic rate was 0.30 mg C m^–3 h^–1 but was lower in the reservoirs than in the temporary ponds and lagoons.     

Evidence for the presence of muscarinic acetylcholine receptors in bovine brain coated vesicles

Evidence obtained from quinuclidinylbenzilate binding determinations suggested that muscarinic acetylcholine receptor molecules are present in purified bovine brain coated vesicles. Immunoprecipitates formed from coated vesicles with polyclonal antibodies to clathrin bound on the surface of fixed Staphylococcus aureus cells also showed quinuclidinylbenzilate binding activity. The high purity of coated vesicles was established by assays for biochemical markers and by electron microscopy. Muscarinic receptor sites for quinuclidinylbenzilate binding to coated vesicles displayed a Kd of 25 pM and a Bmax of about 191 fmol/mg of protein. Binding competition experiments using atropine, N-methylscopolamine, oxotremorine, and carbamylcholine confirmed the typical muscarinic nature of the binding site. Ranking order of potency for the receptors was: atropine greater than N-methylscopolamine greater than oxotremorine greater than carbachol Analysis of data using a two-site model revealed 13% high-affinity sites for oxotremorine, 66% high-affinity sites for carbachol, and 62% for the antagonist N-methylscopolamine. Heterogeneity of binding affinities for muscarinic drugs detected in the coated vesicles may be related to the presence of coated vesicle subpopulations in brain tissue, (Kohtz, D. S., Kohtz, J. D., Schook, W. J., and Puszkin, S. (1985) J. Cell Biol. 101, 48a; Pfeffer, S. R., and Kelly, R. B. (1985) Cell 40, 949-957).     

Evidence for a pool of non-recycling transferrin receptors in peripheral sheep reticulocytes

Sheep reticulocytes from phlebotomized animals have a total transferrin binding potential that may exceed by an order of magnitude the surface binding capacity. Steady state uptake of transferrin at 37 degrees C is generally less than 50% of the total transferrin binding capacity. During long-term incubation of the reticulocytes, all transferrin binding ability is lost, the ability to internalize being lost most rapidly. The loss in ability to bind transferrin during long-term incubation is independent of the number of surface transferrin binding sites, since removal of surface receptors with pronase does not affect the rate of loss of the internal pool of receptors during long-term incubation. Moreover, after removing surface receptors with pronase, only a fraction of the original number of receptors is restored to the surface, despite the presence of a large pool of internal receptors. These data suggest that only a fraction of the internal pool of receptors is capable of recycling to the cell surface in sheep reticulocytes.     

Active and passive respiratory mechanics in anesthetized dogs

In six spontaneously breathing anesthetized dogs (pentobarbital sodium, 30 mg/kg) airflow, volume, and tracheal and esophageal pressures were measured. The active and passive mechanical properties of the total respiratory system, lung, and chest wall were calculated. The average passive values of respiratory system, lung, and chest wall elastances amounted to, respectively, 50.1, 32.3, and 17.7 cmH2O X l-1. Resistive pressure-vs.-flow relationships for the relaxed respiratory system, lung, and chest wall were also determined; a linear relationship was found for the former (the total passive intrinsic resistance averaged 4.1 cmH2O X l-1 X s), whereas power functions best described the others: the pulmonary pressure-flow relationship exhibited an upward concavity, which for the chest wall presented an upward convexity. The average active elastance and resistance of the respiratory system were, respectively, 64.0 cmH2O X l-1 and 5.4 cmH2O X l-1 X s. The greater active impedance reflects pressure losses due to force-length and force-velocity properties of the inspiratory muscles and those due to distortion of the respiratory system from its relaxed configuration.     

The biological activity of cyclopropyl analogs of all-trans- and 13-cis-retinoic acid in the rat vaginal smear assay

The biological activity of a series of cyclopropyl analogs of all-trans- and 13-cis-retinoic acid has been evaluated in the vaginal smear assay carried out in vitamin A-deficient rats. These analogs were designed to probe the role of the 13-cis isomer in the actions of the parent all-trans-retinoic acid by blocking the interconversion of these two compounds. Although relatively less active, the potency of some of the cyclopropyl analogs suggests that 13-cis-retinoic acid is a fully active metabolite of all-trans-retinoic acid. Since 13-cis-retinoic acid represents a small percentage of the retinoic acid metabolites, the physiological significance of this activity is still unclear. Possible reasons for the reduced activity of the cyclopropyl analogs, as well as an aromatic analog of retinoic acid, are discussed.     

3α, 11α-Dihydroxy-23-oxo-lup-20(29)-en-28-oic acid from Acanthopanax trifoliatus

The new triterpene 3α,11α-dihydroxy-23-oxo-lup-20(29)-en-28-oic acid was isolated from Acanthopanax trifoliatus. Its structure has been determined on the basis of spectroscopic data and chemical transformations.     

Effects of hyperthermia on DNA interstrand crosslinking after treatment with BCNU in 9L rat brain tumor cells

The effects of hyperthermia (42 degrees C) on 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU)-mediated DNA interstrand crosslink formation were investigated in 9L rat brain tumor cells using the technique of alkaline elution. When cells were treated with 60 microM BCNU for 1 hr at 37 degrees C and incubated for 6 hr in drug-free medium at 42 degrees C, there was a 50% increase in crosslinking; and when cells were treated at 42 degrees C and incubated at 37 degrees C, there was a 45% increase in crosslinking compared with the results for cells treated and incubated at 37 degrees C. When cells were treated and incubated at 42 degrees C, there was a 129% increase in DNA crosslinking. The same relative order of results was found for cell survival. These results suggest that hyperthermia can increase DNA interstrand crosslink formation and the consequent cell death through two independent mechanisms: an increase in the amount of initial alkylation because of the increased rate of hydrolysis of BCNU at higher temperatures, and the effect of heat on DNA structure that leads to an increase in the number of crosslinks formed.     

Prekallikrein and kininogens in blister fluids in burn patients

Blister fluids removed from benign cutaneous burns contain the components of the prekallikrein-kininogens system in a non activated state. Their occurrence in the fluids is explained by a diffusion from the blood plasma.