Obituary for Professor Robert Harza Burris

Plant and Soil - Winter rapeseed (Brassica napus) is characterized by a low N recovery in seeds and requires high rates of fertilization to maintain yield. Its nutrient use efficiency could be...     

Deleted in breast cancer-1 (DBC-1) in the interface between metabolism,aging and cancer

DBC1 (deleted in breast cancer-1) is a nuclear protein that regulates cellular metabolism. Since alteration in cellular metabolism have been proposed to be the emerging ‘hallmark’ of cancer, it is possible that DBC1 may be implicated in the regulation of cancer cell energy metabolism. However, at this point any role of DBC1 in cancer is only speculative. In this review, we will discuss the new developments in DBC1 research, its molecular structure, regulatory roles and implication in metabolism, aging and cancer.     

Feeding of Acetes paraguayensis (Nobili) (Decapoda: Sergestidae) from the Parana River, Argentina

Feeding habits of Acetes paraguayensis (Hansen) were studied by examining the stomach content of specimens from two lakes. A. paraguayensis is omnivorous, feeding mainly on members of littoral-benthic and lotic communities. Algae, rotifers and microcrustaceans (copepods and cladocerans) are the more frequent items in the bulk of the stomach content. Oligochaeta and Diptera larvae were an alternative food source when available. Shrimp feeding habits difference between the two lakes may be due to the resource availability. A. paraguayensis are trophic linkers between limnetic and lotic habitats with an important role in the transportation of energy from the floodplain to the principal channel in the Paraná Rivers System.     

The Phragmites communis Trin. chromosome complement in the Danube Delta

Summary This study elucidates the caryotypes in two varieties of Phragmites communis of the Danube Delta, by means of an original squash technique.The two varieties studied above coexist in the floating reed biocoenosis, but there exist different masses without any transitory forms. The flavescens and gigantissima varieties have different morphophysiological characteristics, the latter variety flowers later and shows the gigantism characteristics of polyploids.Comparative analysis of the caryotypes of the two varieties shows that the variety gigantissima is probably a natural auto-octopolyploid (2n = 8x = 96) of a relatively recent origin, as the chromosomes can be grouped into units of 4. The origin of the flavescens variety (2n = 4x = 48) is not certain, because the chromosomes can only be grouped in pairs within the caryotype. It seems that this variety, widespread all over the earth, has an older origin, since the rearrangements determining the present configuration of the caryotype occurred at chromosome level.     

Signal transduction in Alzheimer disease: p21-activated kinase signaling requires C-terminal cleavage of APP at Asp664

The deficits in Alzheimer disease (AD) stem at least partly from neurotoxic β-amyloid peptides generated from the amyloid precursor protein (APP). APP may also be cleaved intracellularly at Asp664 to yield a second neurotoxic peptide, C31. Previously, we showed that cleavage of APP at the C-terminus is required for the impairments seen in APP transgenic mice, by comparing elements of the disease in animals modeling AD, with (platelet-derived growth factor B-chain promoter-driven APP transgenic mice; PDAPP) versus without (PDAPP D664A) a functional Asp664 caspase cleavage site. However, the signaling mechanism(s) by which Asp664 contributes to these deficits remains to be elucidated. In this study, we identify a kinase protein, recently shown to bind APP at the C-terminus and to contribute to AD, whose activity is modified in PDAPP mice, but normalized in PDAPP D664A mice. Specifically, we observed a significant increase in nuclear p21-activated kinase (isoforms 1, 2, and or 3; PAK-1/2/3) activation in hippocampus of 3 month old PDAPP mice compared with non-transgenic littermates, an effect completely prevented in PDAPP D664A mice. In contrast, 13 month old PDAPP mice displayed a significant decrease in PAK-1/2/3 activity, which was once again absent in PDAPP D664A mice. Similarly, in hippocampus of early and severe AD subjects, there was a progressive and subcellular-specific reduction in active PAK-1/2/3 compared with normal controls. Interestingly, total PAK-1/2/3 protein was increased in early AD subjects, but declined in moderate AD and declined further, to significantly below that of control levels, in severe AD. These findings are compatible with previous suggestions that PAK may be involved in the pathophysiology of AD, and demonstrate that both early activation and late inactivation in the murine AD model require the cleavage of APP at Asp664.     

A role for p53 in the regulation of lysosomal permeability by delta 9-tetrahydrocannabinol in rat cortical neurones: implications for neurodegeneration

The psychoactive ingredient of marijuana, Δ⁹-tetrahydrocannabinol (Δ⁹-THC), can evoke apoptosis in cultured cortical neurones. Whilst the intracellular mechanisms responsible for this apoptotic pathway remain to be fully elucidated, we have recently identified a role for the CB₁ type of cannabinoid (CB) receptor and the tumour suppressor protein, p53. In the current study, we demonstrate the Δ⁹-THC promotes a significant increase in lysosomal permeability in a dose- and time-dependent manner. The increase in lysosomal permeability was blocked by the CB₁ receptor antagonist, AM251. Δ⁹-THC increased the localization of phospho-p53Ser15 at the lysosome and stimulated the release of the lysosomal cathepsin enzyme, cathepsin-D, into the cytosol. The p53 inhibitor, pifithrin-α and small interfering RNA-mediated knockdown of p53 prevented the Δ⁹-THC-mediated increase in lysosomal permeability. Furthermore, the Δ⁹-THC -mediated induction of apoptosis was abrogated by a cell-permeable cathepsin-D inhibitor (10 μM). Thus, the study demonstrates that Δ⁹-THC impacts on the lysosomal system, via p53, to evoke lysosomal instability as an early event in the apoptotic cascade. This provides evidence for a novel link between the CB₁ receptor and the lysosomal branch of the apoptotic pathway which is crucial in regulating neuronal viability following exposure to Δ⁹-THC.