Chemical magnetoreception: bird cryptochrome 1a is excited by blue light and forms long-lived radical-pairs

Cryptochromes (Cry) have been suggested to form the basis of light-dependent magnetic compass orientation in birds. However, to function as magnetic compass sensors, the cryptochromes of migratory birds must possess a number of key biophysical characteristics. Most importantly, absorption of blue light must produce radical pairs with lifetimes longer than about a microsecond. Cryptochrome 1a (gwCry1a) and the photolyase-homology-region of Cry1 (gwCry1-PHR) from the migratory garden warbler were recombinantly expressed and purified from a baculovirus/Sf9 cell expression system. Transient absorption measurements show that these flavoproteins are indeed excited by light in the blue spectral range leading to the formation of radicals with millisecond lifetimes. These biophysical characteristics suggest that gwCry1a is ideally suited as a primary light-mediated, radical-pair-based magnetic compass receptor.     

Recombinant interleukin-24 lacks apoptosis-inducing properties in melanoma cells

IL-24, also known as melanoma differentiation antigen 7 (mda-7), is a member of the IL-10 family of cytokines and is mainly produced by Th(2) cells as well as by activated monocytes. Binding of IL-24 to either of its two possible heterodimeric receptors IL-20R1/IL-20R2 and IL-22R/IL-20R2 activates STAT3 and/or STAT1 in target tissues such as lung, testis, ovary, keratinocytes and skin. To date, the physiological properties of IL-24 are still not well understood but available data suggest that IL-24 affects epidermal functions by increasing proliferation of dermal cells. In stark contrast to its "normal" and physiological behaviour, IL-24 has been reported to selectively and efficiently kill a vast variety of cancer cells, especially melanoma cells, independent of receptor expression and Jak-STAT signalling. These intriguing properties have led to the development of adenovirally-expressed IL-24, which is currently being evaluated in clinical trials. Using three different methods, we have analysed a large panel of melanoma cell lines with respect to IL-24 and IL-24 receptor expression and found that none of the investigated cell lines expressed sufficient amounts of functional receptor pairs and therefore did not react to IL-24 stimulation with Jak/STAT activation. Results for three cell lines contrasted with previous studies, which reported presence of IL-24 receptors and activation of STAT3 following IL-24 stimulation. Furthermore, evaluating four different sources and modes of IL-24 administration (commercial recombinant IL-24, bacterially expressed GST-IL-24 fusion protein, IL-24 produced from transfected Hek cells, transiently over-expressed IL-24) no induction or increase in cell death was detected when compared to appropriate control treatments. Thus, we conclude that the cytokine IL-24 itself has no cancer-specific apoptosis-inducing properties in melanoma cells.     

Non-invasive assessment of reproductive status in Chinese water deer (Hydropotes inermis): Correlation with sexual behaviour

The annual reproductive cycle of Chinese water deer (Hydropotes inermis), a nearly threatened small cervid species, was studied by means of fecal steroid analysis coupled with behavioural observations. Data showed a clearly seasonal reproductive pattern. In adult males, the onset of androgen secretion, in October, was concomitant with the first manifestations of territoriality. Androgen metabolites concentrations reached significant peak values in December, when matings occurred. In mature females, there was a close synchrony in reproductive states: lactational/seasonal anoestrus from June to November, pregnancy from December to May. Fecal progesterone metabolites profiles suggested that silent ovulations occurred at the onset of breeding season and that females conceived at their first ovulation with behavioural estrus. The female sexual receptivity state might last only a few hours. High levels of sniffing, parades and pursuits, concomitant of the highest concentrations of androgen, could allow the males to detect the furtive estrus in the females present in their territory. We concluded that the non-invasive method applied for the first time in this species was useful for the evaluation of the endocrine status and its relation with behaviour.     

Ecto-alkaline phosphatase considered as levamisole-sensitive phosphohydrolase at physiological pH range during mineralization in cultured fetal calvaria cells

Alkaline phosphatase (ALP) activity expressed on the external surface of cultured fetal rat calvaria cells and its relationship with mineral deposition were investigated under pH physiological conditions. After replacement of culture medium by assay buffer and addition of p-nitrophenyl phosphate (pNPP), the rate of substrate hydrolysis catalyzed by whole cells remained constant for up to seven successive incubations of 10 min and was optimal over the pH range 7.6–8.2. It was decreased by levamisole by a 90% inhibition at 1 mM which was reversible within 10 min, dexamisole having no effect. Values of apparent Km for pNPP were close to 0.1 mM, and inhibition of pNPP hydrolysis by levamisole was uncompetitive (K_i = 45 μM). Phosphatidylinositol-specific phospholipase C (PI-PLC) produced the release into the medium of a p-nitrophenyl phosphatase (pNPPase) sensitive to levamisole at pH 7.8. The released activity whose rate was constant up to 75 min represented after 15 min 60% of the value of ecto-pNPPase activity. After 75 min of PI-PLC treatment the ecto-pNPPase activity remained unchanged despite the 30% decrease in Nonidet P-40-extractable ALP activity. High levels of ⁴⁵Ca incorporation into cell layers used as index of mineral deposition were decreased by levamisole in a stereospecific manner after 4 h, an effect which was reversed within 4 h after inhibitor removal, in accordance with ecto-pNPPase activity variations. These results evidenced the levamisole-sensitive activity of a glycosylphosphatidylinositol-anchored pNPPase consistent with ALP acting as an ecto-enzyme whose functioning under physiological conditions was correlated to ⁴⁵Ca incorporation and permit the prediction of the physiological importance of the enzyme dynamic equilibrium at the cell surface in cultured fetal calvaria cells. © 1996 Wiley-Liss, Inc.