We investigated the effects of acetylcholine (ACh) and histamine on intracellular calcium concentration ([Ca2+]i) and contraction of freshly isolated guinea pig tracheal smooth muscle cells. Previous electrophysiological studies revealed that agonists elicit cation and Cl- currents, but a role for Ca2+ in mediating these effects remains unresolved. Here we characterize agonist-induced changes of [Ca2+]i, using fura 2, and examine the contribution of the sarcoplasmic reticulum (SR) to regulation of [Ca2+]i. We provide evidence that the rise of [Ca2+]i and the contraction elicited by ACh or histamine are largely due to release of Ca2+ from stores. Agonists elicited Ca2+ transients in Ca(2+)-free solution with 0.5 mM ethylene glycol-bis (beta-aminoethyl ether)-N, N, N',N'-tetraacetic acid (EGTA), whereas prolonged exposure to Ca(2+)-free solution diminished the rise of [Ca2+]i. In addition, blockade of SR Ca(2+)-adenosinetriphosphatase (ATPase) by cyclopiazonic acid (CPA) or thapsigargin caused elevation of [Ca2+]i and reduction of ACh-evoked increase of [Ca2+]i. In many cells, [Ca2+]i fell below baseline (undershoot) after ACh or caffeine. CPA abolished this undershoot and reduced the rate of recovery of [Ca2+]i to basal levels. Furthermore, oscillations of [Ca2+]i were elicited in the presence or absence of extracellular Ca2+, and these too were reversibly abolished by CPA. Our results provide evidence that Ca2+ stores play a significant role in agonist-mediated increase of [Ca2+]i in tracheal muscle and that the SR contributes to the restoration of basal Ca2+ levels.

We have shown previously that platelet-activating factor (PAF), a potent inflammatory mediator, acts directly on isolated rat osteoclasts to elevate cytosolic free Ca2+ concentration ([Ca2+]i). The purpose of this study was to examine the effects of PAF on osteoclast function. Osteoclasts were isolated from the long bones of neonatal rabbits and studied in three ways. [Ca2+]i of fura-2-loaded osteoclasts was monitored by microspectrofluorimetry. In 9 out of 16 cells tested, PAF (10-100 nM) caused elevation of [Ca2+]i that peaked then returned to baseline. In contrast, the biologically inactive precursor and metabolite of PAF, lyso-PAF, was without effect. Using time-lapse videomicroscopy, we found that PAF elicited retraction of peripheral pseudopods. Although calcitonin induced sustained retraction and immobility, the response to PAF was transient and, within 30 min, pseudopods reformed. To assess effects of PAF on resorptive activity, osteoclasts were cultured on dentin slices for 48 h in the presence of vehicle, PAF (200 nM), or calcitonin (100 ng/ml). PAF increased the area of individual resorption pits (from control values of 1,660 +/- 110 to 2,240 +/- 200 microns2, P < 0.05) and the total planar area resorbed per unit area of substrate (from 7.6 +/- 1.6 to 14.5 +/- 3.1 x 10(4) microns2/cm2, P < 0.025). As expected, calcitonin significantly decreased resorptive activity. These data indicate that PAF activates osteoclastic resorption. PAF may play a role in mediating the resorption of bone and mineralized cartilage in inflammatory diseases such as rheumatoid arthritis and periodontitis.

We demonstrated previously that platelet-activating factor (PAF), a potent inflammatory mediator, acts on osteoclasts to elevate cytosolic [Ca2+] and stimulate resorption. However, it is not clear whether the effects of PAF on resorptive activity are direct or indirect. In the present study, we investigated the effects of PAF on osteoclast motility. Osteoclasts were isolated from the long bones of neonatal rabbits, and cell motility and morphology were monitored using time-lapse video microscopy. Calcitonin, a hormone known to induce retraction of pseudopods and inhibit resorptive activity, was used to render osteoclasts quiescent. Within 10 minutes of calcitonin treatment (100 ng/ml, final), pronounced retraction of pseudopods was observed in 68 of 112 cells tested. When PAF (200 nM, final) was added 10 minutes after calcitonin treatment, pseudopods were evident 1 h later in 15 of 37 calcitonin-responsive cells tested. In contrast, pseudopods were evident in only 4 of 31 calcitonin-responsive cells treated with control solutions (PAF-vehicle or S-PAF, the biologically inactive stereoisomer of PAF). Pseudopod formation was quantified by measuring the planar area of pseudopods with a computer-based video analysis system. When assessed 60 minutes following PAF treatment, the pseudopod area was significantly greater in PAF-treated cells than in control cells. In some calcitonin-treated osteoclasts, PAF induced pseudopod formation when applied focally using an extracellular micropipette, consistent with a direct action of PAF. We conclude that PAF directly induces pseudopod formation in calcitonin-inhibited osteoclasts, a morphologic response indicative of osteoclast activation.

The purpose of this study was to meet the regulations of “natural product”, fermented celery powder (FCP) were selected in this research to evaluate its ability to restrain Listeria monocytogenes growth in the naturally cured sausage, and also the effectiveness on quality and sensory attributes of the sausages. The content of nitrite is 150mg/kg in each group. The FCP were assessed at both their intrinsic pH and at a pH adjusted approach that of a sausage product. The results are the FCP treatments can substitute conventional sodium nitrite to the growth of Listeria monocytogenes in the sausage without negatively impact the quality and sensory attributes of the products. In addition, the adjusted FCP treatments were more effective than conventional nitrite.