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Biomedical subjects

T W Bell

Publications and source records attributed to T W Bell.

8 recordsLinked to original sources

Carriers and channels: current progress and future prospects.

Recent advances in the understanding of biological transport and in the design of artificial transport systems have resulted from the structural elucidation of the K+ ion channel and from synthesis of artificial receptors for cations and anions, as well as neutral and zwitterionic organic molecules. Sensors, gated carriers, and self-assembling capsules and nanotubes are all important offsprings of current efforts to mimic natural transport across biomembranes.

Cations

Detection of creatinine by a designed receptor.

An artificial receptor has been designed to bind creatinine with a color change (chromogenic response) caused by proton transfer from one end of the receptor to the other. The receptor was synthesized and found to extract creatinine from water into chlorocarbon solvents. The color change in the organic layer is specific for creatinine relative to other organic solutes, and it is selective for creatinine relative to sodium, potassium, and ammonium ions. The chromogenic mechanism is revealed by x-ray crystal structures of creatinine, the free receptor, and the complex, showing "induced fit" binding resulting from electronic complementarity between host and guest.

Acridines

Self-assembly of a double-helical complex of sodium.

Spontaneous self-organization of helical and multiple-helical molecular structures occurs on several levels in living organisms. Key examples are alpha-helical polypeptides, double-helical nucleic acids and helical protein structures, including F-actin, microtubules and the protein sheath of the tobacco mosaic virus. Although the self-assembly of double-helical transition-metal complexes bears some resemblance to the molecular organization of double-stranded DNA, selection between monohelical, double-helical and triple-helical structures is determined largely by the size and geometrical preference of the tightly bound metal. Here we present an example of double-helical assembly induced by the weaker and non-directional interactions of an alkali-metal ion with an organic ligand that is pre-organized into a coil. We have characterized the resulting complex by two-dimensional NMR and fast-atom-bombardment mass spectrometry. These results provide a step toward the creation of molecular tubes or ion channels consisting of intertwined coils.

Magnetic Resonance Spectroscopy

Sex pheromones of two Asian moths (Creatonotos transiens, C. gangis; Lepidoptera--Arctiidae): behavior, morphology, chemistry and electrophysiology.

Two sympatric species of Asian arctiid moths (Creatonotos spp.) use a sequential, dual luring and mating system. After sunset males pneumatically expand their coremata from a cavity between the abdominal sternites 7 and 8 and release their pheromone. They attract other males and thus, scent-emitting male groups may develop. About 30 min later females are attracted to the calling males. Upon contact with a female the male's corema deflates and mating follows. After 1-2 h the male calling subsides and now the remaining virgin females continue to emit their pheromone bouquet from internal, tubular glands located in the dorsal part of the abdomen, rostrad from tergite 8/9. This attracts males and further matings occur.- The coremata are huge, pneumatically eversible organs composed of two pairs of tubes, up to 37 mm long, each covered by ca. 3000 scent hairs (scales). There is a giant epidermal (trichogen) gland cell at the base of each hair. One large corema may contain up to 0.5 mg of the pheromone, hydroxydanaidal. The internal, tubular female glands are antler shaped; their air-filled lumen is ventilated by abdominal pumping. The major components of the female attractant are (Z,Z,Z)-3,6,9-heneicosatriene and (Z,Z)-2 (2,5-octadienyl)-3-undecyloxirane with different ratios in the two species. One of the minor components, common to both species, is (Z,Z,Z)-3,6,9-tricosatriene. Only the male antennae possess specialized receptor cells for the female attractants; other antennal cells of both sexes respond to the male pheromone.

Animals

Unrecognized Legionnaires' disease as a cause of fatal illness.

Lungs from 224 patients, obtained at autopsy, were examined for Legionella pneumophila by fluorescent antibody (FA) staining. Of 121 patients who died with pneumonia, L pneumophila was present in eight cases (6.6%). (Two of the eight patients exhibited no important respiratory symptoms or fever, although pneumonia contributed considerably to their deaths. Preexisting underlying disease was present in all cases. Legionnaires' disease (LD), endemic in the central Ohio area, may cause up to 3.6% of the nosocomial pneumonias at the study site. Application of the local incidence of LD to the number of annual adult deaths in the United States indicates that many LD-associated deaths may occur each year. The study shows the importance of using the FA and Dieterle stains during routine pathological examination of lung tissue, especially from compromised hosts in endemic areas.

Adult