Calcium leak from intracellular stores--the enigma of calcium signalling

Wherever you travel through the cytoplasm of the cells you will find organelles with internal [Ca(2+)] levels higher than in the surrounding cytosol. This is particularly true of the endoplasmic reticulum (ER) (or sarcoplasmic reticulum (SR) in muscle cells); such organelles serve as the main sources of releasable Ca(2+) for cytosolic cellular signalling. Calcium pumps of the SERCA family (sarcoplasmic and endoplasmic reticulum calcium ATP-ases) import calcium into the organelle lumen. The other mechanism that is responsible for the steady state calcium level within the lumen of ER or SR is a calcium leak that balances the influx created by the pumps. The leak remains the most enigmatic of the processes involved in calcium regulation. The molecular nature of the leak mechanism is not known. The basal leak is a relatively slow process, which is difficult to investigate and which is easily outmatched (both in the amplitude of calcium responses and in attractiveness to experimenters) by substantially faster second messenger-induced release. Nevertheless, information on the properties of the calcium leak, although thinly scattered through the pages of PubMed, has been slowly accumulating. In this review we will discuss the properties of the calcium leak and speculate about possible mechanisms, which could mediate this process.

A multivariable analysis of factors influencing mucositis after autologous progenitor cell transplantation

Mucositis is a common and vexing complication of autologous progenitor cell transplantation (ABMT). A modified oral mucositis assessment scale (OMAS) has been found to be a reproducible and effective tool for monitoring mucositis after radiation therapy or chemotherapy. We utilized the modified OMAS scale to study clinical parameters associated with the development of mucositis in 79 patients undergoing ABMT. Median patient age was 52; 61% had non-Hodgkin's lymphoma (NHL), 23% multiple myeloma and 14% Hodgkin's disease. Patients were mobilized with G-CSF alone or the combination of etoposide plus G-CSF. Univariable correlates of worse mucositis were prior radiation therapy (P = 0.004), a diagnosis of NHL (P = 0.014), progenitor cell mobilizing regimen containing etoposide (P = 0.001), and ABMT preparative regimen containing etoposide (P = 0.006). Multivariable regression analysis revealed that NHL diagnosis (P = 0.007), prior radiation therapy (P = 0.001), and etoposide in the mobilizing regimen (P = 0.034) were associated with worse post-transplant mucositis. Worsening mucositis correlated with a longer inpatient length of stay. We conclude that several variables contribute to worsening mucositis during autologous transplantation, including etoposide in the progenitor cell mobilizing regimen.