Apolipoprotein D expression in human brain reactive astrocytes.

Astrocytosis is a hallmark of damage that frequently occurs during aging in human brain. Astrocytes proliferate in elderly subjects, becoming hypertrophic and highly immunoreactive for glial fibrillary acidic protein (GFAP). These cells are one type that actively responds in the repair and reorganization of damage to the neural parenchyma and are a source of several peptides and growth factors. One of these biomolecules is apolipoprotein D (apo D), a member of the lipocalin family implicated in the transport of small hydrophobic molecules. Although the role of apo D is unknown, increments in brain apo D expression have been observed in association with aging and with some types of neuropathology. We have found an overexpression of apo D mRNA in reactive astrocytes by in situ hybridization in combination with immunohistochemistry for apo D in normal aged human brains. The number of double-labeled cells varied according to the cerebral area and the gliosis grade. The possible significance of this increased synthesis of apo D in reactive astrocytes is discussed in relation to the role of apo D in aging and in glial function.     

The critical role of alpha‐folate receptor in the resistance of melanoma to methotrexate

Although methotrexate (MTX) is an effective drug for several types of cancer, it is not active against melanoma. Experiments following methotrexate treatment indicated a reduced accumulation of the drug in the cytosolic compartment in melanoma cells, suggesting that the mechanisms that control the transport and retention of this drug could be altered in melanoma. For this reason, we analyzed the presence and function of folate receptor‐α (FRα) in melanoma cells. In this study, we have identified the presence of FRα in normal and pathological melanocytes and demonstrated that MTX is preferentially transported through this receptor in melanoma cells. FRα‐induced endocytic transport of MTX, together with drug melanosomal sequestration and cellular exportation, ensures reduced accumulation of this cytotoxic compound in intracellular compartments. The critical role of FRα in this mechanism of resistance and the therapeutic consequences of these findings are also discussed.     

The cost of ant attendance and melezitose secretion in the black bean aphid Aphis fabae

1. The aphid Aphis fabae (Scopoli) is facultatively tended by Lasius niger (Linnaeus) ants. Previously, we found that A. fabae colonies can be made up of several clones, and that clones display significant differences in the composition of their honeydew sugars, especially in the amount of the ant attractant sugar melezitose that they produce. 2. These clonal differences could greatly impact the strength of the mutualistic interaction with ants as well as the aphids' fitness. 3. Hence, the aim of this study was to compare the fitness of different A. fabae clones that differed in their melezitose secretion, and whether or not they were tended by ants. 4. Individual fitness indices, colony growth, and alate production of single‐clone aphid colonies were analysed. 5. The results demonstrate that the fitness consequences of ant attendance critically depend on an interaction between levels of melezitose production. In particular, we show that high‐melezitose secreting clones produce fewer alates and hence might have a lower dispersal ability in the presence of ants. 6. Furthermore, these data confirm previous evidence that ant attendance is costly and results in the production of fewer apterae.     

Glycoproteins from Bufo arenarum vitelline envelope with fertility-impairing effect on homologous spermatozoa

When spermatozoa from Bufo arenarum are incubated with molecules extracted from the vitelline envelopes of homologous oocytes, they lose their fertilizing capacity. Those molecules are glycoproteins, and the elimination of mannoside residues from them results in activity loss, while digestion of the proteic moiety did not alter their biological effect. Sepharose-concanavalin A columns were used to purify the glycoproteins, since the active fraction binds to the column. The fertility-impairing effect observed does not seem to be mediated by an acrosome reaction-inducing effect.