Selection on incremental variation of eye size in a wild population of Daphnia.

Several studies of eye morphology have analysed macroevolutionary patterns in the diversity of eyes, and although these studies are often linked to environment or behaviour, they provide only indirect evidence of selection. Specific data to show the microevolutionary potential for adaptation by natural selection in eye morphology have been lacking. We document directional selection on eye size, an important determinant of visual capabilities, in a wild population of the freshwater microcrustacean Daphnia. We show that even slight changes in eye size may have major consequences for fitness. An increase in eye diameter of 19.9 µm - slightly more than one standard deviation - is associated with an increase in clutch size of one egg, or an increase of nearly 20% of the mean clutch size. Furthermore, relative eye size is genetically variable and thus could evolve in response to the observed selective pressure. We conclude that selection on incremental variation in eye size may have led to differences observed on broader taxonomic scales.

Celastrol inhibits aminoglycoside-induced ototoxicity via heat shock protein 32.

Hearing loss is often caused by death of the mechanosensory hair cells of the inner ear. Hair cells are susceptible to death caused by aging, noise trauma, and ototoxic drugs, including the aminoglycoside antibiotics and the antineoplastic agent cisplatin. Ototoxic drugs result in permanent hearing loss for over 500,000 Americans annually. We showed previously that induction of heat shock proteins (HSPs) inhibits both aminoglycoside- and cisplatin-induced hair cell death in whole-organ cultures of utricles from adult mice. In order to begin to translate these findings into a clinical therapy aimed at inhibiting ototoxic drug-induced hearing loss, we have now examined a pharmacological HSP inducer, celastrol. Celastrol induced upregulation of HSPs in utricles, and it provided significant protection against aminoglycoside-induced hair cell death in vitro and in vivo. Moreover, celastrol inhibited hearing loss in mice receiving systemic aminoglycoside treatment. Our data indicate that the major heat shock transcription factor HSF-1 is not required for celastrol-mediated protection. HSP32 (also called heme oxygenase-1, HO-1) is the primary mediator of the protective effect of celastrol. HSP32/HO-1 inhibits pro-apoptotic c-Jun N-terminal kinase (JNK) activation and hair cell death. Taken together, our data indicate that celastrol inhibits aminoglycoside ototoxicity via HSP32/HO-1 induction.

Combinations of 4-hydroperoxycyclophosphamide (4-HC) and cisplatin for bone marrow purging in autologous marrow transplantation: an update.

We are studying the usefulness of combinations of 4-HC and cisplatin as a potential purging regimen for autologous bone marrow transplantation. In all of our studies, in vitro cytotoxicity was determined by clonogenic assay, and drug interaction was quantitated using the multiple drug-effect analysis method. The cells were incubated for one hour (4-HC) and/or 4 hours (cisplatin). We found that the drugs in combination had cytotoxic synergism against human leukemia cell lines (K-562 and Raji). The synergism was sequence-dependent (cells must be exposed to 4-HC first), was present at various molar ratios of the drugs, and most pronounced at high levels of cell kill. We also found that the drugs had cytotoxic synergism against normal human marrow progenitors (CFU-GM). However, the leukemic cells were approximately 55 times more sensitive to the combination than CFU-GM. In a murine system, the drugs were synergistic against L1210 leukemia cells and normal murine CFU-GM, but L1210 cells were at least 130 times more sensitive to the combination than CFU-GM. To determine the ability of L1210 cells to grow in vivo after exposure to the drugs, BDF1 mice were injected with 2 x 10(4) cells which had been incubated with 4-HC and/or cisplatin. The survival time of untreated controls was 13 +/- 2.8 days. For treated groups, the cure rates after 50 days of observation were 33% (4-HC, 40 uM), 0% (cisplatin, 8 uM), and 100% (4-HC + cisplatin). Finally, at concentrations resulting in equivalent toxicity to marrow CFU-GM, cisplatin seemed to be more toxic to murine spleen blast colony forming cells (CFC-BC) than 4-HC. The drugs in combination appeared to have at least additive toxicities against CFC-BC.

In vitro synergism of 4-hydroperoxycyclophosphamide and cisplatin: relevance for bone marrow purging.

Autologous bone marrow transplantation with 4-hydroperoxycyclophosphamide (4-HC)-purged bone marrow gives long-term remission in almost half of relapsed acute nonlymphocytic leukemia and non-Hodgkin's lymphoma patients, but relapse of disease is the main cause of failure, suggesting ineffective purging in some cases. Cisplatin (CP) has activity against a variety of human tumors and is not commonly used for initial therapy of leukemia and lymphoma. Using established human leukemia cell lines, combinations of 4-HC and CP were investigated as a potential regimen for improving the ex vivo removal of leukemia cells from bone marrow. The cell lines (K-562 and Raji) were incubated for 1 (4-HC) or 4 h (CP), washed, and assayed for inhibition of colony formation in semisolid media. In both cell lines, CP (4h) was more potent than 4-HC (1 h). Combinations of the drugs in various molar ratios were studied after the cells were sequentially incubated with 4-HC and CP. The effects of the drugs were analyzed using the multiple drug-effect analysis of Chou and Talalay. Analysis of data on in vitro inhibition of colony formation suggested that all combinations studied were synergistic in both cell lines, with the greatest synergism being found in the Raji cell line. In addition, for K-562 cells we could detect at least a 4.6 log reduction in cloning with the CP:4-HC combination (1:10 molar ratio). We conclude that CP is a potential candidate in drug combinations for ex vivo bone marrow purging because of its high potency against human leukemia cell lines, its synergistic activity in combination with 4-HC, and its ability to reduce a high tumor burden when combined with 4-HC.