Distinct role for CD8 T cells toward cutaneous tumors and visceral metastases

The growth of immunogenic tumors in immunocompetent individuals is one of the oldest conundrums in tumor immunology. Although the ability of mouse CD8+ T cells to control transplanted tumors is well documented, little is known about their impact on autochthonous tumors. To gain insight into the role of CD8+ T cells during the course of cancer development, we produced a novel model of spontaneous melanoma. The metallothionein (MT)-ret/AAD mouse is transgenic for the RET oncogene and the chimeric MHC molecule AAD (alpha1-alpha2 domains of HLA-A2 linked to alpha3 domain of H2-Dd). This model recapitulates the natural history of human melanoma, and expression of the AAD molecule makes it suitable for analyzing CD8+ T cell responses directed against peptide Ags that have been previously identified in HLA-A2+ melanoma patients. We found that, as tumors grow, mice develop a broad melanoma-specific CD8+ T cell response. Occurrence of cutaneous nodules is not affected by CD8+ T cell depletion, showing that although CD8+ T cells are functional, they have no effect on established cutaneous tumors. However, depleted mice die from visceral disease much earlier than controls, showing that CD8+ T cells control metastasis spreading and disease progression. Antigenic modulation is observed in visceral metastases, suggesting that visceral nodules may be subject to immunoediting. Our data demonstrate that growth of melanoma in the MT-ret/AAD model involves several tolerance mechanisms sequentially. They also reveal a different role for CD8+ T cells toward early stage of cutaneous tumors and late visceral metastatic stage of the disease.     

The ‘shifting baseline’ phenomenon: a global perspective

In this paper we demonstrate that low level ‘artisanal’ fishing can dramatically affect populations of slow-growing, late-maturing animals and that even on remote oceanic islands, stocks have been depleted and ecosystems degraded for millennia. Industrialised fisheries have developed during different decades in different regions of the world, and this has almost always been followed by a period of massive stock decline. However, ecosystems were not pristine before the onset of industrial fishing and it is difficult to assess the ‘virgin’ state of a population given that it may have been subject to moderate or even high levels of fishing mortality for many centuries. A wide range of information is available to help define or deduce historic marine population status. These include ‘traditional’ written sources but also less conventional sources such as archaeological remains, genetic analyses or simple anecdotal evidence. Detailed information, collected specifically for the purpose of determining fish stock biomass tends to exist only for recent decades, and most fishery assessments around the world (and thus time-series of biomass estimates), are less than 30 years long. Here we advocate using a wider range of multidisciplinary data sources, although we also recognise that it can be difficult to separate natural variability associated with changing climatic conditions from human-induced changes through fishing. We consider whether or not recovery of degraded ecosystems is ever possible and discuss a series of one-way ratchet like processes that can make it extremely difficult to return to a former ecosystem state.     

Time-Resolved FTIR Studies of Sensory Rhodopsin II (NpSRII) from Natronobacterium pharaonis: Implications for Proton Transport and Receptor Activation

The photocycle of the photophobic receptor from Natronobacterium pharaonis, NpSRII, is studied by static and time-resolved step-scan Fourier transform infrared spectroscopy. Both low-temperature static and time-resolved spectra resolve a K-like intermediate, and the corresponding spectra show little difference within the noise of the time-resolved data. As compared to intermediate K of bacteriorhodopsin, relatively large amide I bands indicate correspondingly larger distortions of the protein backbone. The time-resolved spectra identify an intermediate L-like state with surprisingly small additional molecular alterations. With the formation of intermediate M, the Schiff-base proton is transferred to the counterion Asp-75. This state is characterized by larger amide bands indicating larger distortions of the protein. We can identify a second M state that differs only in small-protein bands. Reisomerization of the chromophore to all-trans occurs with the formation of intermediate O. The accelerated decay of intermediate M caused by azide results in another red-shifted intermediate with a protonated Schiff base. The chromophore in this state, however, still has 13-cis geometry. Nevertheless, the reisomerization is still as slow as under the conditions without azide. The results are discussed with respect to mechanisms of the observed proton pumping and the possible roles of the intermediates in receptor activation.     

The Anabolic Androgenic Steroid Nandrolone Decanoate Disrupts Redox Homeostasis in Liver,Heart and Kidney of Male Wistar Rats

The abuse of anabolic androgenic steroids (AAS) may cause side effects in several tissues. Oxidative stress is linked to the pathophysiology of most of these alterations, being involved in fibrosis, cellular proliferation, tumorigenesis, amongst others. Thus, the aim of this study was to determine the impact of supraphysiological doses of nandrolone decanoate (DECA) on the redox balance of liver, heart and kidney. Wistar male rats were treated with intramuscular injections of vehicle or DECA (1 mg.100 g⁻¹ body weight) once a week for 8 weeks. The activity and mRNA levels of NADPH Oxidase (NOX), and the activity of catalase, glutathione peroxidase (GPx) and total superoxide dismutase (SOD), as well as the reduced thiol and carbonyl residue proteins, were measured in liver, heart and kidney. DECA treatment increased NOX activity in heart and liver, but NOX2 mRNA levels were only increased in heart. Liver catalase and SOD activities were decreased in the DECA-treated group, but only catalase activity was decreased in the kidney. No differences were detected in GPx activity. Thiol residues were decreased in the liver and kidney of treated animals in comparison to the control group, while carbonyl residues were increased in the kidney after the treatment. Taken together, our results show that chronically administered DECA is able to disrupt the cellular redox balance, leading to an oxidative stress state.     

Bioenergetics of the Archaea.

In the late 1970s, on the basis of rRNA phylogeny, Archaea (archaebacteria) was identified as a distinct domain of life besides Bacteria (eubacteria) and Eucarya. Though forming a separate domain, Archaea display an enormous diversity of lifestyles and metabolic capabilities. Many archaeal species are adapted to extreme environments with respect to salinity, temperatures around the boiling point of water, and/or extremely alkaline or acidic pH. This has posed the challenge of studying the molecular and mechanistic bases on which these organisms can cope with such adverse conditions. This review considers our cumulative knowledge on archaeal mechanisms of primary energy conservation, in relationship to those of bacteria and eucarya. Although the universal principle of chemiosmotic energy conservation also holds for Archaea, distinct features have been discovered with respect to novel ion-transducing, membrane-residing protein complexes and the use of novel cofactors in bioenergetics of methanogenesis. From aerobically respiring Archaea, unusual electron-transporting supercomplexes could be isolated and functionally resolved, and a proposal on the organization of archaeal electron transport chains has been presented. The unique functions of archaeal rhodopsins as sensory systems and as proton or chloride pumps have been elucidated on the basis of recent structural information on the atomic scale. Whereas components of methanogenesis and of phototrophic energy transduction in halobacteria appear to be unique to Archaea, respiratory complexes and the ATP synthase exhibit some chimeric features with respect to their evolutionary origin. Nevertheless, archaeal ATP synthases are to be considered distinct members of this family of secondary energy transducers. A major challenge to future investigations is the development of archaeal genetic transformation systems, in order to gain access to the regulation of bioenergetic systems and to overproducers of archaeal membrane proteins as a prerequisite for their crystallization.     

A Non-hydrolyzable ATP Derivative Generates a Stable Complex in a Light-inducible Two-component System

Isothermal calorimetry (ITC) measurements yielded the binding constants during complex formation of light-inducible histidine kinases (HK) and their cognate CheY-type response regulators (RR). HK-RR interactions represent the core function of the bacterial two-component system, which is also present in many bacterial phytochromes. Here, we have studied the recombinant forms of phytochromes CphA and CphB from the cyanobacterium Tolypothrix PCC7601 and their cognate RRs RcpA and RcpB. The interaction between the two reaction partners (HK and RR) was studied in the presence and absence of ATP. A complex formation was observable in the presence of ATP, but specific interactions were only found when a non-hydrolyzable ATP derivative was added to the mixture. Also, the incubation of the HK domain alone (expressed as a recombinant protein) with the RR did not yield specific interactions, indicating that the HK domain is only active as a component of the full-length phytochrome. Considering also previous studies on the same proteins (Hübschmann, T., Jorissen, H. J. M. M., Börner, T., Gärtner, W., and de Marsac, N. (2001) Eur. J. Biochem. 268, 3383–3389) we now conclude that the HK domains of these phytochromes are active only when the chromophore domain is in its Pr form. The formerly documented phosphate transfer between the HK domain and the RR takes place via a transiently formed protein-protein complex, which becomes detectable by ITC in the presence of a non-hydrolyzable ATP derivative. This finding is of interest also in relation to the function of some (blue light-sensitive) photoreceptors that carry the HK domain and the RR fused together in one single protein.