Effects of acetone, methanol, or paraformaldehyde on cellular structure, visualized by reflection contrast microscopy and transmission and scanning electron microscopy

The authors recently showed variable subcellular immunoreactivity of the Bcl-2 and Bax proteins after fixation of cell monolayers with acetone, methanol, or paraformaldehyde (PF) followed by methanol (PF/methanol). Here, the authors demonstrate by reflection contrast microscopy and transmission electron microscopy that acetone or methanol fixation result in complete loss of integrity of intracellular structures in contrast with PF or glutaraldehyde fixation. Scanning electron microscopy revealed poor preservation of plasma membrane integrity after fixation in acetone or methanol. Fixation with PF before methanol reduced damage to intracellular and plasma membranes. In addition, Western blot analysis demonstrated loss of Bcl-2 and Bax protein during acetone or methanol fixation, whereas PF fixation before methanol permeabilization markedly reduced this loss. For studies on the intracellular localization of soluble or unknown types of antigen, the authors discourage the use of acetone and methanol as single fixatives.

Routine formaldehyde fixation irreversibly reduces immunoreactivity of Bcl-2 in the nuclear compartment of breast cancer cells, but not in the cytoplasm

Bcl-2 and Bax belong to a family of proteins involved in apoptosis regulation and are believed to reside in the cellular cytoplasm. The authors recently reported interphase nuclear localization of both proteins after immunofluorescence staining of formaldehyde- and methanol-fixed human and rodent cell monolayers. In addition, the authors' data confirmed earlier reports on Bcl-2 immunoreactivity of mitotic chromosomes in human cells. In their experience, nuclear or mitotic staining of Bcl-2, in contrast with cytoplasmic Bcl-2 immunoreactivity, is rarely observed in formaldehyde-fixed, paraffin-embedded breast cancer specimens. Therefore, the authors wondered if nuclear and mitotic Bcl-2 immunoreactivity could be irreversibly reduced by certain fixation procedures, including formaldehyde fixation. Here the authors investigated the effects of various routinely used fixation protocols and antigen retrieval techniques on Bcl-2 and Bax immunoreactivity in monolayers of MCF-7 human breast cancer cells. Whereas nuclear and mitotic immunoreactivity for Bcl-2 was clearly present after formaldehyde and methanol fixation, it was completely absent in cells fixed in acetone, methanol, or formaldehyde alone. In addition, it was found that in particular nuclear and mitotic Bcl-2, and to a lesser extent cytoplasmic Bcl-2 immunoreactivity, decreased after prolonged formaldehyde fixation, whereas Bax immunoreactivity diminished only slightly. Heat-mediated antigen retrieval after prolonged formaldehyde fixation elevated cytoplasmic, but not nuclear and mitotic, Bcl-2 immunoreactivity.

Development of resistance to glutathione depletion-induced cell death in CC531 colon carcinoma cells: association with increased expression of bcl-2

The glutathione (GSH) level of CC531 rat colorectal cancer cells is readily decreased by exposure to buthionine sulfoximine (BSO), an inhibitor of GSH synthesis; at 25 microM BSO, these cells died in a non-apoptotic fashion. By continuous exposure of CC531 cells to increasing concentrations of BSO, we obtained a BSO-resistant cell line (CCBR25) that was 50 times more resistant to BSO than the parental cell line. Whereas the GSH content of CCBR25 and CC531 cells was similar, the former contained a much higher level of the Bcl-2 protein. After stable transfection of CC531 cells with the human bcl-2 gene, the resulting Bcl-2-overexpressing cell line appeared to be 9 times more resistant to BSO than the parental cell line. These findings suggest that the Bcl-2 protein offers resistance against the cytotoxic effect of severe GSH depletion.

Decreased exposure to saquinavir in HIV-1-infected patients after long-term antiretroviral therapy including ritonavir and saquinavir

OBJECTIVE

To explore whether steady-state plasma pharmacokinetics of ritonavir and saquinavir change during long-term treatment in HIV-1-infected patients on antiretroviral treatment including ritonavir and saquinavir.

METHODS

The pharmacokinetics of ritonavir and saquinavir were assessed during an 8-h period on two occasions in six HIV-1 infected patients on stable twice daily treatment with ritonavir 400 mg, saquinavir 400 mg and stavudine 40 mg with or without lamivudine 150 mg twice daily.

RESULTS

The first study day was 4-12 months (median 7 months) after the start of the current regimen. The second study day was 9-15 months (median 10 months) later. No significant differences were observed for the ritonavir pharmacokinetics between the first and second study day. However, median change in plasma trough level of saquinavir between the two study days was -30% (range -79 to +11%; P = 0.06). Median change in maximum plasma concentration was -40% (range -62 to +34%; P = 0.09). The median change in area under the plasma concentration versus time curve over 0-8 h was -33% (range -53 to +21%; P = 0.06).

CONCLUSION

The exposure to saquinavir decreased over time in HIV-infected patients on stable antiretroviral therapy. These data suggest that regular monitoring of plasma drug concentrations should become part of routine patient care even in apparently compliant patients.

Corticosterone regulates expression of BDNF and trkB but not NT-3 and trkC mRNA in the rat hippocampus

Corticosterone has profound effects on growth, differentiation, and synaptic transmission of hippocampal neurons by activation of mineralocorticoid receptors (MRs) and glucocorticoid receptors (GRs). In the present study we tested if neurotrophins can be implicated in these effects. For this purpose we injected 30, 300, and 1,000 microg corticosterone s.c. (per kg body weight) in adrenalectomized rats and measured the mRNA levels of brain-derived neurotrophic factor (BDNF), tyrosine receptor kinase (trk)B, neurotrophin (NT)-3, and trkC in hippocampal cell fields at 6 hr after steroid administration by in situ hybridization. NT-3 and trkC mRNA did not show significant changes in any hippocampal region after the various doses of corticosterone. BDNF mRNA decreased after corticosterone administration dose dependently, resulting in a maximal suppression of 35, 20, and 50% in dentate gyrus, CA3, and CA1, respectively. Interestingly, trkB responded to corticosterone in an inverted U-shaped fashion in CA3 and dentate gyrus: the low dose of corticosterone increased trkB mRNA expression in both regions by approximately 30%, while the effect of the two higher doses was not different from the vehicle injected controls. In conclusion, we found differential effects of low and high doses of corticosterone on BDNF and trkB expression in hippocampus, which suggests involvement of a coordinated MR- and GR-mediated action.