Morphology and distribution of taste papillae and oral denticles in the developing oropharyngeal cavity of the bamboo shark, Chiloscyllium punctatum.

Gustation in sharks is not well understood, especially within species that ingest food items using suction. This study examines the morphological and immunohistochemical characterisation of taste papillae and oral denticles in the oropharynx of the brown-banded bamboo shark Chiloscyllium punctatum and compares their distribution during development. Taste papillae of the brown-banded bamboo shark Chiloscyllium punctatum are located throughout the oropharyngeal region and are most concentrated on the oral valves (2,125-3,483 per cm(2) in embryos; 89-111 per cm(2) in mature adults) close to the tooth territories. Papillae appearance is comparable at all stages of development, with the exception of the embryos (unhatched specimens), where no microvilli are present. Oral valve papillae are comparable in structure to Type I taste buds of teleost fishes, whereas those of the rest of the oropharyngeal region are comparable to Type II. Both types of papillae show immunofluorescence for a number of markers of taste buds, including β-Catenin and Sox2. Taste papillae densities are highest in embryos with 420-941 per cm(2) compared to 8-29 per cm(2) in mature adults. The total number of papillae remains around 1,900 for all stages of development. However, the papillae increase in diameter from 72±1 µm in embryos to 310±7 µm in mature individuals. Microvilli protrude in multiple patches at the apical tip of the papilla covering ∼0.5% of the papillar surface area. We further document the relationship between taste papillae and the closely associated oral denticles within the shark orophayngeal cavity. Oral denticles first break through the epithelium in the antero-central region of the dorsal oral cavity, shortly after the emergence of teeth, around time of hatching. Denticles are located throughout the oropharyngeal epithelium of both immature and mature stages, with the highest concentrations in the antero-dorsal oral cavity and the central regions of the pharynx. These denticle-rich areas of the mouth and pharynx are therefore thought to protect the epithelium, and importantly the taste papillae, from abrasion since they correlate with regions where potential food items are processed or masticated for consumption. Taste papillae and denticles are more dense in anterior oropharyngeal regions in close association with the oral jaws and teeth, and in the juvenile/hatchling shark taste units are functional, and innervated, allowing the shark to seek out food in utero, at birth or on emergence from the egg case

"Low-state" Black Hole Accretion in Nearby Galaxies

I summarize the main observational properties of low-luminosity AGNs in nearby galaxies to argue that they are the high-mass analogs of black hole X-ray binaries in the "low/hard" state. The principal characteristics of low-state AGNs can be accommodated with a scenario in which the central engine is comprised of three components: an optically thick, geometrically accretion disk with a truncated inner radius, a radiatively inefficient flow, and a compact jet.Comment: 8 pages. To appear in From X-ray Binaries to Quasars: Black Hole Accretion on All Mass Scales, ed. T. J. Maccarone, R. P. Fender, and L. C. Ho (Dordrecht: Kluwer

Efimov Trimers near the Zero-crossing of a Feshbach Resonance

Near a Feshbach resonance, the two-body scattering length can assume any value. When it approaches zero, the next-order term given by the effective range is known to diverge. We consider the question of whether this divergence (and the vanishing of the scattering length) is accompanied by an anomalous solution of the three-boson Schr\"odinger equation similar to the one found at infinite scattering length by Efimov. Within a simple zero-range model, we find no such solutions, and conclude that higher-order terms do not support Efimov physics.Comment: 8 pages, no figures, final versio

Supermassive Binaries and Extragalactic Jets

Some quasars show Doppler shifted broad emission line peaks. I give new statistics of the occurrence of these peaks and show that, while the most spectacular cases are in quasars with strong radio jets inclined to the line of sight, they are also almost as common in radio-quiet quasars. Theories of the origin of the peaks are reviewed and it is argued that the displaced peaks are most likely produced by the supermassive binary model. The separations of the peaks in the 3C 390.3-type objects are consistent with orientation-dependent "unified models" of quasar activity. If the supermassive binary model is correct, all members of "the jet set" (astrophysical objects showing jets) could be binaries.Comment: 31 pages, PostScript, missing figure is in ApJ 464, L105 (see http://www.aas.org/ApJ/v464n2/5736/5736.html

Long-Baseline Neutrino Facility (LBNF) and Deep Underground Neutrino Experiment (DUNE) Conceptual Design Report Volume 2: The Physics Program for DUNE at LBNF

The Physics Program for the Deep Underground Neutrino Experiment (DUNE) at the Fermilab Long-Baseline Neutrino Facility (LBNF) is described

L'importance relative des ruptures α(C—C) et β(C—H) dans la photolyse du propène et de l'isobutène à 184,9 NM

La photolyse du propène et de l'isobutène purs, et en présence d’oxygène à 184,9 nm sous des pressions variant de 5 à 100 Torr a été réétudiée. Plusieurs produits allant du méthane aux C6 dans le cas du propène et aux C8 dans le cas de l'isobutène ont été observés. L'effet de pression est beaucoup plus important dans la photolyse de l’isobutène. Les rendements quantiques de tous les produits plus lourds que les monomères sont inférieurs à 0,01 lorsque ceux-ci sont éclairés en présence de 10% d'oxygène. Les fragmentations principales de la molécule photoexcitée impliquent la rupture des liaisons α(C-C) et β(C-H). Dans le cas du propène le rapport de ces deux ruptures est de 0,57 (σ = 0,054) et de 0,95 (σ = 0,10) dans celui de l'isobutène. On n'observe pas d'effets de longueur d’onde entre 174 et 184,9 nm

Cycloaddition routes to polycyclic quinones: Part 1 boron triacetate as a regiochemical directing agent

9-Hydroxy-1,4-anthraquinone, a benzannelated juglone derivative, undergoes regiospecific cycloaddition with isoprene when conducted in the presence of boron triacetate. The structure of this regiomer has been determined by X-ray crystallography.Richard A. Russell, Geoffrey J. Collin, Meta Sterns, Ronald N. Warrene

An economical and versatile synthesis of 5,8-dialkoxy-2-acetyl-3,4-dihydronaphthalenes: key precursors for the synthesis of chiral anthracyclines

5,8-Diacetoxy-2-acetyl-3,4-dihydronaphthalene, prepared by a new route from the Diels–Alder adduct of buta-1,3-diene and p-benzoquinone, is selectively deacetylated (Cs2CO3 in tetrahydrofuran or K2CO3 in dimethyl sulphoxide) to intermediates suitable for use in chiral anthracycline synthesis.Richard A. Russell, Geoffrey J. Collin, Paul S. Gee and Ronald N. Warrene

Essential oils of Hedeoma mandoniana Wedd and of Minthostachys andina (Brett) Epling

Meeting: Produits naturels d'origine végétale, 16-19 mai 1989, Montréal, Qué., CAReprin