Morphological characteristics facilitating stimulus access and removal in the olfactory organ of the spiny lobster, Panulirus argus: insight from the design

The olfactory organ (antennule) of the spiny lobster, Panulirusargus, has from 1000–2000 olfactory sensilla (aesthetascs)which are grouped in a dense tuft along the distal portion ofthe lateral filament. This assemblage of aesthetascs, togetherwith other associated sensilla, forms a substantial boundarylayer through which odor stimuli must diffuse in moving to andfrom the aesthetascs. Periodic flicking of the antennule, abehavior analogous to sniffing in certain vertebrate species,is considered to be a means of reducing the thickness of thisboundary layer. In this report we describe the structure ofthe aesthetasc tuft and examine certain of its dynamic properties.We propose that the unique configuration of the aesthetasces,together with their orientation, serves to channel water flowbetween these sensilla during a flick, thereby reducing diffusiondistances and consequently facilitating the access and removalof odor stimuli in a rapid, synchronized manner. The functionalsignificance of this and other design features of the aesthetasctuft is considered in light of the current understanding offundamental olfactory process.     

Double-antibody radioimmunoassay for staphylococcal enterotoxins A and B

A sensitive double-antibody radioimmunoassay for staphylococcal enterotoxins A and B is described. The separation of the primary antigen-antibody complex of enterotoxin A and B was achieved with an anti-rabbit gamma globulin from goats. Radioiodinated aggregate fractions of staphylococcal enterotoxins exhibited reduced immunological activity and showed little competition with non-radioactive exterotoxin. The radioimmunoassay was successfully applied for the quantitation of enterotoxins in food.     

Respiratory evaporation in panting fowl: Partition between the respiratory and buccopharyngeal pumps

Summary Ventilation (V) and respiratory water loss were measured in domestic fowlGallus gallus subjected to raised environmental temperatures (33±2°C) and breathing air, 8% O₂ in N₂, 3% CO₂ in air or 5% CO₂ in air. Birds breathing air underwent an 18.6-fold increase in respiratory frequency and a 5-fold reduction in tidal volume and panting was accompanied by vigorous gular flutter. Hypoxic and hypercapnic birds breathed more slowly and deeply and gular flutter was strongly inhibited. The ratio was similar to that predicted on the basis of the measured ventilation assuming saturation of expired gas at measured gular mucosal temperature in hypoxic and hypercapnic birds but 54% greater than the predicted value in birds panting in air. It is concluded that the excess water loss during normal panting results from tidal airflow generated independently by the buccopharyngeal pump and that buccopharyngeal ventilation is equivalent to 54% of the respiratory ventilation.     

Formation of N-Pyroglutamyl Peptides from N-Glu and N-Gln Precursors in Aplysia Neurons

Abstract : Matrix-assisted laser desorption/ionization with time-of-flight mass spectrometry is used to examine the formation of N -pyroglutamate (pGlu) in single, identified neurons from Aplysia . Six pGlu peptides are identified in the R3-14 and the R15 neurons that result from in vivo processing of peptides containing either Glu or Gln at their respective N-termini. Moreover, we show that Glu-derived pGlu is not a sample collection or measurement artifact. The pGlu peptides are detected in isolated cell bodies, regenerated neurites in culture, interganglionic connective nerves, cell homogenates, and collected releasates. We also demonstrate that R3-14 cells readily convert a synthetic N -Glu peptide to its pGlu analogue, indicating the presence of novel enzymatic activity.     

Doublecortin is a microtubule-associated protein and is expressed widely by migrating neurons.

Doublecortin (DCX) is required for normal migration of neurons into the cerebral cortex, since mutations in the human gene cause a disruption of cortical neuronal migration. To date, little is known about the distribution of DCX protein or its function. Here, we demonstrate that DCX is expressed in migrating neurons throughout the central and peripheral nervous system during embryonic and postnatal development. DCX protein localization overlaps with microtubules in cultured primary cortical neurons, and this overlapping expression is disrupted by microtubule depolymerization. DCX coassembles with brain microtubules, and recombinant DCX stimulates the polymerization of purified tubulin. Finally, overexpression of DCX in heterologous cells leads to a dramatic microtubule phenotype that is resistant to depolymerization. Therefore, DCX likely directs neuronal migration by regulating the organization and stability of microtubules.