Goblet cell degranulation in isolated canine tracheal epithelium: response to exogenous ATP, ADP, and adenosine

Mucin secretion by goblet cells was determined by quantifying degranulation events (DE) in isolated, superficial epithelium from canine trachea. The epithelium was isolated and explanted to a novel transparent, permeable support, and the goblet cells were visualized by video microscopy. Baseline degranulation events were quantified at 0.05 DE/min. Luminal ATP (10(-4) M, n = 10) stimulated a biphasic secretory response; a burst, maximum rate = 87.9 +/- 25.3, was followed by a plateau, rate = 1.9 +/- 0.3 DE/min. Serosal ATP elicited a complex set of responses: 9 cells failed to respond, 13 exhibited a trivial response, and 31 responded vigorously but with highly variable patterns of degranulation. Nonhydrolyzable 5'-adenylylimidodiphosphate caused degranulation from both sides of the epithelium. Luminal ADP and adenosine were ineffective. Serosal ADP and adenosine elicited a range of responses that was similar in diversity and magnitude to the ATP response. Our conclusions were as follows: 1) goblet cells in the superficial epithelium of the airway can be studied at the single-cell level in explants; 2) nucleotides stimulate goblet cells to secrete mucin; and 3) the goblet cell expresses different nucleotide receptors on its apical and basolateral membranes.

Magnetic Development of Flaring Regions at Centimeter Wavelengths

It has been known for many years that the flare build-up manifests at centimeter wavelengths (2-6 cm), in the form of increased intensity and increased polarization of the active region. The flare-associated bursts originate in these intense sources, and the probability of occurrence of bursts increases with the increasing intensity of these narrow bright regions. With the availability of arc-second resolution using the VLA it has been possible to study the nature of this build-up from two-dimensional synthesized maps over short periods before the start of a flare. For a hard x-ray associated impulsive 6 cm burst observed on June 25, 1980 (Kundu, Schmahl, and Velusamy 1981), we produced several 15-minute synthesized maps in total intensity (I) and polarization (V) just before the flare onset (Kundu 1981). Figure 1 shows the central 11x16 regions of 15 minute synthesis maps over the period 14:45-15:45 UT. As can be seen from these Figures, the region is very complex, consisting of numerous components many of which are bipolar. These components have brightness temperatures of 6-9x106 K during the hour before the flare. The burst source was located close to the neutral line of these oppositely polarized regions near B. The burst maximum is identified, with a “+” and the burst extent averaged over the period 1551-1600 UT is shown by the dotted contour in the last map.

Thermonuclear Processes on Accreting Neutron Stars

The observed properties of X-ray burst sources have recently been reviewed by Lewin and Clark (1980) and Lewin and Joss (1980). About thirty-five such sources are presently known, and they have a spatial distribution reminiscent of stellar Population II (see Figure 1). The salient features of these sources include burst rise times of ≲ls, decay time scales of ~3–100 s, peak luminosities of ~1039 ergs per burst, spectra that can generally be well fitted by blackbody emission from a surface with a constant effective radius of ~10 km and a peak temperature of ~3 × 107 K, and “tails” of softer X-ray emission that may persist for several minutes after the burst maximum. Profiles of bursts from some typical burst sources are shown in Figure 2. The intervals between bursts from a given source may be regular or erratic and are typically in the range of ~104−105 s; many sources undergo burst-inactive phases that can last for weeks or months. Most burst sources are also sources of persistent X-ray emission, and the ratio of average persistent luminosity to time-averaged burst luminosity is typically ~102 during burst-active phases. (The properties of the “Rapid Burster,” MXB1730-335, are different from those of all other known burst sources and will be discussed separately in §VI below.) There are few correlations among the burst flux, burst intervals, and persistent X-ray flux from any given source, and the detailed burst shapes vary from one source to another and often vary with time in a given source.

Spectral Association of the 7 August 1972 Solar Radio Burst with Particle Acceleration

(Solar Phys.). Microwave burst data from the August 7, 1972 event recorded on nine discrete frequencies between 245 and 35000 MHz at the Sagamore Hill Radio Observatory (Figure 1) provide a basis for correlation studies (especially timing information) of the associated white light flare, the high energy particle emission, type II bursts, and many other phenomena. This is perhaps the first time that sufficient radio coverage (i.e., data above 10000 MHz) was available to obtain the spectral slope information (related to electron-energy distribution) which is inherent in this part of the spectrum. Heretofore, timing was related to burst flux density profile variations. Improved correlations resulted from shorter centimeter wavelength data which supplied more accurate timing information than that derived from Hα observations. The shape and intensity of the burst peak flux density spectrum has also been used for qualitative analysis of energetic particle and white light events. The ultimate good may possibly come from spectral analysis of the minute by minute variation of the burst microwave radiation spectral slope α (above fmax) in the area between 15000 and 35000 MHz. This may be used alone or in relation to the position of fmax, where fmax is the frequency of burst maximum emission at a given time. This is basically our present investigation.