Links between apoptosis, proliferation and the cell cycle.

Many physiological processes, including proper tissue development and homeostasis, require a balance between apoptosis and cell proliferation. All somatic cells proliferate via a mitotic process determined by progression through the cell cycle. Apoptosis (programmed cell death) occurs in a wide variety of physiological settings, where its role is to remove harmful, damaged or unwanted cells. Apoptosis and cell proliferation are linked by cell-cycle regulators and apoptotic stimuli that affect both processes. This review covers recent developments in the field and examines new evidence of the interconnection between apoptosis and cell proliferation.

Induction of apoptosis in myeloid progenitors by granulocyte-macrophage colony-stimulating factor.

Spontaneous apoptosis of normal purified bone marrow CD34+ cells induced by granulocyte-macrophage colony-stimulating factor (GM-CSF) via the Fas pathway appears to be mediated by caspase-1 and caspase-8 activity. In seeking an alternative explanation for this observation, the present study examined CD34+ cell growth with different cytokines, cytokine concentrations, caspase inhibitors, cell crowding and different media. Exposure of the normal CD34+ cells to different concentrations of GM-CSF and granulocyte colony-stimulating factor (G-CSF) increased apoptosis at lower concentrations. However, these GM-CSF effects were suppressed by G-CSF. Investigation of the association between apoptosis and crowding and different media showed that: 1) G-CSF and GM-CSF are equally effective as survival factors, and 2) the percentage of apoptotic cells in liquid culture was markedly lower than that found in methylcellulose culture. Finally, immunofluorescence staining showed that Fas was expressed at 10 ng/mL GM-CSF, while Bcl-2 expression was detected at 100 ng/mL. These findings suggest that cytokine concentration, cell culture conditions, cell crowding and cell interactions all are important factors in GM-CSF-induced apoptosis.

Impact of new AABB guidelines on hepatitis B and C testing among Saudi blood donors.

This study aims to compare the advantages and disadvantages of implementing the new American Association of Blood Banks (AABB) guidelines for hepatitis B and C against its old criteria for screening blood donors. Between July 1995 and December 2002, 63,368 consecutive blood donors were screening for hepatitis B and C according to the new guidelines. Cost and prevalence were analysed and compared with those found using the old AABB guidelines prior to July 1995. The overall percentage rate of deferred donors showed a significantly decrease to 19.3% in 2002, compared to 58.4% before July 1995 (P < 0.001). The new prevalence of hepatitis B and C among Saudi blood donors was found to be 1.7% and 0.6%, respectively, compared to 4% and 1.4%, respectively, under the old AABB guidelines. This resulted in a significant increase in the number and yield of blood units, and a decrease in the prevalence of hepatitis B and C was observed among screened donors. Using the new AABB guidelines, the estimated direct cost of donor screening for hepatitis B and C decreased significantly from 42.8 dollars per donor to 29.2 dollars per donor (P<0.001).