LWR1 and LWR2 are required for osmoregulation and osmotic adjustment in Arabidopsis

With the goal of identifying molecular components of the low-water-potential response, we have carried out a two-part selection and screening strategy to identify new Arabidopsis mutants. Using a system of polyethylene glycol-infused agar plates to impose a constant low-water-potential stress, putative mutants impaired in low-water-potential induction of the tomato (Lycopersicon esculentum) le25 promoter were selected. These lines were then screened for altered accumulation of free Pro. The seedlings of 22 mutant lines had either higher or lower Pro content than wild type when exposed to low water potential. Two mutants, designated low-water-potential response1 (lwr1) and lwr2, were characterized in detail. In addition to higher Pro accumulation, lwr1 seedlings had higher total solute content, greater osmotic adjustment at low water potential, altered abscisic acid content, and increased sensitivity to applied abscisic acid with respect to Pro content. lwr1 also had altered growth and morphology. lwr2, in contrast, had lower Pro content and less osmotic adjustment leading to greater water loss at low water potential. Both lwr1 and lwr2 also had altered leaf solute content and water relations in unstressed soil-grown plants. In both mutants, the effects on solute content were too large to be explained by the changes in Pro content alone, indicating that LWR1 and LWR2 affect multiple aspects of cellular osmoregulation.     

Strategies for choosing between alternatives with different attributes: exemplified by house-hunting ants

We tested the decision-making abilities of emigrating ant colonies. The colonies had to choose a new nest site when presented with two or more potential nest sites, each with different attributes or different combinations of attributes. For Leptothorax albipennis colonies in the laboratory, darkness of the nest cavity, internal height of the cavity and width of the entrance were all important attributes. The colonies ranked these attributes: darkness of the nest site was more important than internal cavity height, which in turn was more important than entrance width. These choices conform to the logic of transitivity. In addition, the colonies used a sophisticated decision-making strategy in which they took all alternatives and all attributes into consideration. Furthermore, the ants, in effect, weighed the different values of different attributes. They also chose the best nest when presented with only one excellent nest among four mediocre ones or one excellent nest in an array of one excellent, one good and one mediocre. Altogether, our results suggest that these ant colonies, in deciding upon a new home, used a weighted additive strategy, one of the most computationally expensive and thorough decision-making strategies. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.      

Dietary supplementation with cysteine prodrugs selectively restores tissue glutathione levels and redox status in protein-malnourished mice(1)

Protein malnutrition (PM) is a major health problem in the world. PM compromises antioxidant defense in the body. In particular, PM decreases tissue glutathione (GSH) levels. A high protein diet was found to restore tissue GSH levels in animal studies, however it is not recommended for the early phase of PM rehabilitation. Therefore, using dietary supplementation to restore tissue GSH without giving a high protein diet may be an adjunct therapy that helps improve antioxidant status during the early rehabilitation of PM. In this study, we systematically compared the efficacy of dietary supplementation of four cysteine prodrugs: N-acetylcysteine, L-2-oxo-4-thiazolidine-carboxylate, methionine, and GSH, on tissue GSH in mice fed a protein-deficient (0.5%) diet. Results showed that dietary supplementation of cysteine prodrugs to PM mice restored GSH levels in liver, lung, heart and spleen, but not in colon. GSH and GSSG levels in brain and kidney were not affected by cysteine prodrug or PM. Supplementation also restored the redox status in liver and heart (based on GSH/GSSG), and in liver and spleen (based on GSSG/2GSH reduction potential). This suggests that the restoration of GSH levels and redox status by cysteine prodrugs are tissue-specific, and that the two indicators of redox status are not always interchangeable. However, all four prodrugs exhibited similar GSH-enhancing capacities, showing no prodrug-specificity as seen in cell culture studies. In conclusion, this study provided information that may be useful in a clinical setting where a short-term oral supplementation of cysteine prodrugs is necessary for the early rehabilitation of PM patients.     

Lepocreadiidae (Digenea) from the batfish of the genus Platax Cuvier (Teleostei: Ephippidae) from the southern Great Barrier Reef,Queensland, Australia

The following species are described from Platax spp.: Neomultitestis aspidogastriformis n. sp., from P. teira, off Heron Island, Queensland, which can be distinguished from its congeners by the transversely elongate ventral sucker divided into three loculi and probably by testis number; Multitestis magnacetabulum Mamaev, 1970, from P. teira, off Heron Island, Queensland; Diploproctodaeum rutellum (Mamaev, 1970), from P. teira, off Heron Island, Queensland; Diploproctodaeum tsubameuo n. sp., from P. batavianus, from the Swain Reefs, off Queensland, which differs from its congeners in its overlapping, posteriorly attenuated testes and 38-55 ovarian lobes; and Diplocreadium sp., from P. batavianus, from the Swain Reefs, off Queensland.     

Cellular response of antioxidant metalloproteins in Cu/Zn SOD transgenic mice exposed to hyperoxia

Ceruloplasmin, metallothionein, and ferritin are metal-binding proteins with potential antioxidant activity. Despite evidence that they are upregulated in pulmonary tissue after oxidative stress, little is known regarding their influence on trace metal homeostasis. In this study, we have used copper- and zinc-containing superoxide dismutase (Cu/Zn SOD) transgenic-overexpressing and gene knockout mice and hyperoxia to investigate the effects of chronic and acute oxidative stress on the expression of these metalloproteins and to identify their influence on copper, zinc, and iron homeostasis. We found that the oxidative stress-mediated induction of ceruloplasmin and metallothionein in the lung had no effect on tissue levels of copper, iron, or zinc. However, Cu/Zn SOD expression had a marked influence on hepatic copper and iron as well as circulating copper homeostasis. These results suggest that ceruloplasmin and metallothionein may function as antioxidants independent of their role in trace metal homeostasis and that Cu/Zn SOD functions in copper homeostasis via mechanisms distinct from its superoxide scavenging properties.