Chlorhexidine-induced apoptosis or necrosis in L929 fibroblasts: A role for endoplasmic reticulum stress

Chlorhexidine (CHX), widely used as antiseptic and therapeutic agent in medicine and dentistry, has a toxic effect both in vivo and in vitro. The intrinsic mechanism underlying CHX-induced cytotoxicity in eukaryotic cells is, however, still unknown. A recent study from our laboratory has suggested that CHX may induce death in cultured L929 fibroblasts via endoplasmic reticulum (ER) stress. This hypothesis was further tested by means of light and electron microscopy, quantification of apoptosis and necrosis by flow cytometry, fluorescence visualization of the cytoskeleton and endoplasmic reticulum, and evaluation of the expression of 78-kDa glucose-regulated protein 78 (Grp78), a marker of activation of the unfolded protein response (UPR) in cultured L929 fibroblasts. Our finding showing increased Grp 78 expression in CHX-treated cells and the results of flow cytometry, cytoskeleton and endoplasmic reticulum fluorescence visualization, and scanning and transmission electron microscopy allowed us to suggest that CHX elicits accumulation of proteins in the endoplasmic reticulum, which causes ER overload, resulting in ER stress and cell death either by necrosis or apoptosis. It must be pointed out, however, that this does not necessarily mean that ER stress is the only way that CHX kills L929 fibroblasts, but rather that ER stress is an important target or indicator of cell death induced by this drug. (C) 2008 Elsevier Inc. All rights reserved.

Effect of remifentanil hydrochloride administered via constant rate infusion on the minimum alveolar concentration of isoflurane in cats

Objective-To evaluate the effects of increasing doses of remifentanil hydrochloride administered via constant rate infusion (CRI) on the minimum alveolar concentration (MAC) of isoflurane in cats. Animals-6 healthy adult cats. Procedures-For each cat, 2 experiments were performed (2-week interval). On each study day, anesthesia was induced and maintained with isoflurane; a catheter was placed in a cephalic vein for the administration of lactated Ringer`s solution or remifentanil CRIs, and a catheter was placed in the jugular vein for collection of blood samples for blood gas analyses. On the first study day, individual basal MAC (MAC(Basal)) was determined for each cat. On the second study day, 3 remifentanil CRIs (0.25, 0.5, and 1.0 mu g/kg/min) were administered (in ascending order); for each infusion, at least 30 minutes elapsed before determination of MAC (designated as MAC(R0.25`) MAC(R0.5`) and MACR(R1.0`) respectively). A 15-minute washout period was allowed between CRIs. A control MAC (MAC Control) was determined after the last remifentanil infusion. Results-Mean +/- SD MAC(Basal) and MAC(Control) values at sea level did not differ significantly (1.66 +/- 0.08% and 1.52 +/- 0.21%, respectively). The MAC values determined for each remifentanil CRI did not differ significantly. However, MACR(0.25`) MAC(R0.5`) and MAC(R1.0) were significantly decreased, compared with MAC(Basal`) by 23.4 +/- 79%, 29.8 +/- 8.3%, and 26.0 +/- 9.4%, respectively. Conclusions and Clinical Relevance-The 3 doses of remifentanil administered via CRI resulted in a similar degree of isoflurane MAC reduction in adult cats, indicating that a ceiling effect was achieved following administration of the lowest dose. (Am J Vet Res 2009;70:581-588)

Remote probe microphone measurement to verify hearing aid performance

We assessed the feasibility of obtaining probe microphone measurements of hearing aids at a distance. Face-to-face and remote probe microphone measurements were carried out in 60 hearing aid users (mean age 67 yrs) with uni- or bilateral hearing losses (105 ears tested). The participant and a facilitator were located in a room equipped with a probe microphone system interfaced to a PC. Desktop videoconferencing and application sharing was used to allow an audiologist in another room to instruct the facilitator and control the equipment via the LAN. There were significant correlations between face-to-face and remote real ear unaided response (REUR), aided response (REAR) and insertion gain (REIG) at seven discrete frequencies from 250 to 6000 Hz. Differences between face-to-face and remote responses were within the reported variability for probe microphone measurements themselves. The results show that remote probe microphone measurements are feasible and might improve the quality of public hearing aid services and professional training in Brazil.

gamma-Radiation induces apoptosis via sarcoplasmatic reticulum in guinea pig ileum smooth muscle cells

We investigated the effects of gamma-radiation on cells isolated from the longitudinal smooth muscle layer of the guinea pig ileum, a relatively radioresistant tissue. Single doses (up to 50 Gy) reduced the amount of sarcoplasmatic reticulum and condensed the myofibrils, as shown by electron microscopy 3 days post-irradiation. After that, contractility of smooth muscle strips was reduced. Ca(2+) handling was altered after irradiation, as shown in fura-2 loaded cells, with elevated basal intracellular Ca(2+), reduced amount of intrareticular Ca(2+), and reduced capacitive Ca(2+) entry. Radiation also induced apoptosis, judged from flow cytometry of cells loaded with proprium iodide. Electron microscopy showed that radiation caused condensation of chromatin in dense masses around the nuclear envelope, the presence of apoptotic bodies, fragmentation of the nucleus, detachment of cells from their neighbors, and reductions in cell volume. Radiation also caused activation of caspase 12. Apoptosis was reduced by the administration of the caspase inhibitor Z-Val-Ala-Asp-fluoromethyl-ketone methyl ester (Z-VAD-FIVIK) during the 3 day period after irradiation, and by the chelator of intracellular Ca(2+), 1,2-bis(o-aminophenoxy)ethane-N,N,N`,N`-tetraacetic acid (BAPTA), from 1 h before until 2 h after irradiation. BAPTA also reduced the effects of radiation on contractility, basal intracellular Ca(2+), amount of intrareticular Ca(2+), capacitative Ca(2+) entry, and apoptosis. In conclusion, the effects of gamma radiation on contractility, Ca(2+) handling, and apoptosis appear due to a toxic action of intracellular Ca(2+). Ca(2+)-induced damage to the sarcoplasmatic reticulum seems a key event in impaired Ca(2+) handling and apoptosis induced by gamma-radiation. (c) 2008 Elsevier B.V. All rights reserved.