Archaeal phylogeny based on ribosomal proteins

Until recently, phylogenetic analyses of Archaea have mainly been based on ribosomal RNA (rRNA) sequence comparisons, leading to the distinction of the two major archaeal phyla: the Euryarchaeota and the Crenarchaeota. Here, thanks to the recent sequencing of several archaeal genomes, we have constructed a phylogeny based on the fusion of the sequences of the 53 ribosomal proteins present in most of the archaeal species. This phylogeny was remarkably congruent with the rRNA phylogeny, suggesting that both reflected the actual phylogeny of the domain Archaea even if some nodes remained unresolved. In both cases, the branches leading to hyperthermophilic species were short, suggesting that the evolutionary rate of their genes has been slowed down by structural constraints related to environmental adaptation. In addition, to estimate the impact of lateral gene transfer (LGT) on our tree reconstruction, we used a new method that revealed that 8 genes out of the 53 ribosomal proteins used in our study were likely affected by LGT. This strongly suggested that a core of 45 nontransferred ribosomal protein genes existed in Archaea that can be tentatively used to infer the phylogeny of this domain. Interestingly, the tree obtained using only the eight ribosomal proteins likely affected by LGT was not very different from the consensus tree, indicating that LGT mainly brought random phylogenetic noise. The major difference involves organisms living in similar environments, suggesting that LGTs are mainly directed by the physical proximity of the organisms rather than by their phylogenetic proximity.     

On the conceptual difficulties in rooting the tree of life

Rooting the 'tree of life' represents a major challenge for evolutionists. Without such a root, many of the first steps in biological evolution cannot be reconstructed. However, the nature of the last common ancestor of all living beings remains elusive, proof of the difficulty in shedding light on such an ancient event. Here, we highlight the practical difficulties and conceptual reasons that hinder the placement of a universal root. We discuss how, when addressing the question of the root of the tree of life, scientists unconsciously risk using the reasoning pattern of ancient skeptics, unfortunately known only to lead to further uncertainty. Hence, we argue that the root of the tree of life will not be established unless radically new approaches are considered. We propose a hypothetical means to overcome several of the conceptual difficulties pointed out, and suggest that a so-called 'transition analysis' of the structural evolution of the cytoplasmic membrane might be helpful, especially if evolutionary steps involving the rooting issue are polarized accounting more for physicochemical knowledge rather than hypothetical and controversial selective advantages.     

Tumor necrosis factor is a survival and proliferation factor for human myeloma cells

Interleukin-6 (IL-6) is a major survival factor for malignant plasma cells. In patients with multiple myeloma (MM), cell lines whose survival and proliferation are dependent upon addition of exogenous IL-6 have been obtained. We show here that tumor necrosis factor-alpha (TNF-alpha) is also a survival factor for myeloma cell lines, although less potent than IL-6. The survival activity of TNF-alpha is not affected by anti-IL-6 or anti-gp130 monoclonal antibodies (mAbs). TNF-alpha also induces myeloma cells in the cell cycle and promotes the long-term growth of malignant plasma cell lines. As TNF-alpha is produced in patients with MM and associated with a poor prognosis, these results suggest that anti-TNF-alpha therapies could be useful in this disease.     

Experience with antirabies vaccination of foxes using the oral route coordinated among several European countries and perspectives on the use of recombinant vaccinia-rabies virus

Campaigns of fox vaccination against rabies were carried out in Belgium, grand-duchy of Luxembourg and France in September 1986, June and September 1987. The SAD B19 attenuated strain of rabies virus, contained in baits (Tübingen baits) was used as vaccine. Baits were distributed at a range density of 11 to 15 baits per km2. First results are very encouraging. A recombinant vaccinia virus harbouring the rabies virus glycoprotein gene has been developed. This recombinant virus can be given to the fox by the oral route and protects it against rabies virus challenge; it is also innocuous for the fox and other non-target European species. A first trial of fox vaccination against rabies using this recombinant vaccinia-rabies virus has been carried out in Belgium, on a military domain, in October 1987.     

Etude morphologique de Syphatineria pearsi (Baylis, 1928) (Oxyuridae,Nematoda)

Syphatineria (Africanoxys) pearsi (Baylis, 1928) was described from an African squirrel, Heliosciurus rufobrachium (Waterhouse), in Nigeria. This species is re-described from specimens collected in an Heliosciurus gambianus (Ogilby) captured in Zaire. The morphological and biological characteristics of the subgenus Africanoxys Hugot, 1981 are discussed. The subgenus Africanoxys is specific to African rain forest squirrels and, based upon the lengths of the spicule and gubernaculum, two different groups can be distinguished in this subgenus. The first group is parasitic in the Funambulini and the second one is parasitic in the Protoxerini and in Aethosciurus poensis (A. Smith). Although the taxonomic status of genus Aethosciurus is controversial, Parasitology allows us to relate Aethosciurus to the Protoxerini rather than to the Funambulini.

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Etude morphologique de Syphatineria pearsi (Baylis, 1928) (Oxyuridae, Nematoda)

Résumé Syphatineria (Africanoxys) pearsi (Baylis, 1928), un oxyure décrit chez un écureuil africain, Heliosciurus rufobrachium (Waterhouse), au Nigéria, est redécrit à partir d'un matériel collecté chez un Heliosciurus gambianus (Ogilby), capturé au Zaire. Les caractéristiques du sous-genre Africanoxys Hugot, 1981 sont ensuite discutées. Le sous-genre Africanoxys est spécifique des écureuils du bloc forestier congolais. On peut distinguer deux groupes dans le sous-genre d'après la longueur du spicule et celle du gubernaculum. Les parasites du premier groupe ont tous pour hôtes des Funambulini. Les parasites du deuxième groupe ont pour hôtes des Protoxerini et Aethosciurus poensis (A. Smith). La parasitologie apporte donc des arguments à l'hypothèse d'un rapprochement d'Aethosciurus poensis (dont la position systématique est controversée), avec les Protoxerini plutôt qu'avec les Funambulini.

     

Use of recombinant vaccinia-rabies glycoprotein virus for oral vaccination of wildlife against rabies: innocuity to several non-target bait consuming species

The pathogenicity of a vaccinia recombinant virus expressing the rabies glycoprotein (VVTGgRAB) was tested in several wild animal species which could compete with the natural rabies host, the red fox (Vulpes vulpes) in consuming vaccine baits in Europe. The following species were included in this study: wild boar (Sus scrofa), Eurasian badger (Meles meles), wood mouse (Apodemus sylvaticus), yellow-necked mouse (Apodemus flavicollis), bank vole (Clethrionomys glareolus), common vole (Microtus arvalis), field vole (Microtus agrestis), water vole (Arvicola terrestris), common buzzard (Buteo buteo), kestrel (Falco tinnunculus), carrion crow (Corvus corone), magpie (Pica pica) and jay (Garrulus glandarius). During the observation period, the 107 animals given the VVTGgRAB vaccine orally did not show any clinical signs. Daily monitoring for 28 days and postmortem examination did not result in the detection of pox lesions in the oral mucosa or the skin in mammals or the unfeathered portions of birds. VVTGgRAB seems to multiply in the mammalian species tested, since rabies seroconversion was observed in all of them. Birds failed to develop demonstrable rabies virus-neutralizing antibody. A seroconversion against vaccinia virus was observed in two of four wild boars. Serological results obtained in badgers and wild boars also demonstrates the absence of direct or indirect horizontal transmission of the recombinant virus. The potential of the recombinant virus for the immunization of badgers against rabies also was investigated. Only 50% of the badgers orally administered with 1 x 10(8.3) TCID50 of this vaccine were protected against rabies.     

Screening of Chagas disease using ELISA. Comparison of 2 antigens

After proving, in a previous study, the efficiency of immunoenzymology (ELISA) and a primary antigen of Trypanosoma cruzi in the screening of blood donors suffering from Chagas' disease, here the authors show the benefit of the microsomial fraction of this parasite as an antigen. For comparison, it was studied with another primary antigen, Trypanosa, used initially in the adjuvant treatment of cancers, and applied here to the screening of this disease.     

Study on the pathophysiology of experimental Burkholderia pseudomallei infection in mice

Burkholderia pseudomallei is the etiological agent of melioidosis, a potentially fatal disease occurring in man and animals. The aim of this study was to investigate the pathophysiological course of experimental melioidosis, and to identify the target organs, in an animal model. For this purpose SWISS mice were infected intraperitoneally with the virulent strain B. pseudomallei 6068. The bacterial load of various organs was quantified daily by bacteriological analysis and by an enzyme-linked immunosorbent assay (ELISA) based on a monoclonal antibody specific to B. pseudomallei exopolysaccharide (EPS). Electron microscopic investigation of the spleen was performed to locate the bacteria at the cellular level. In this model of acute melioidosis, B. pseudomallei had a marked organ tropism for liver and spleen, and showed evidence of in vivo growth with a bacterial burden of 1.6x10(9) colony forming units (CFU) per gram of spleen 5 days after infection with 200 CFU. The highest bacterial loads were detected in the spleen at all time points, in a range from 2x10(6) to 2x10(9) CFU g(-1). They were still 50-80 times greater than the load of the liver at the time of peak burden. Other investigated organs such as lungs, kidneys, and bone marrow were 10(2)-10(4)-fold less infected than the spleen, with loads ranging from 3x10(2) to 3x10(6) CFU g(-1). The heart and the brain were sites of a delayed infection, with counts in a range from 10(3) to 10(7) times lower than bacterial counts in the spleen. The EPS-specific ELISA proved to be highly sensitive, particularly at the level of those tissues in which colony counting on agar revealed low contamination. In the blood, EPS was detected at concentrations corresponding to bacterial loads ranging from 8x10(3) to 6x10(4) CFU ml(-1). Electron microscopic examination of the spleen revealed figures of phagocytosis, and the presence of large numbers of intact bacteria, which occurred either as single cells or densely packed into vacuoles. Sparse figures suggesting bacterial replication were also observed. In addition, some bacteria could be seen in vacuoles that seemed to have lost their membrane. These observations provide a basis for further investigations on the pathogenesis of the disease.     

The human growth hormone receptor. Secretion from Escherichia coli and disulfide bonding pattern of the extracellular binding domain

A gene fragment encoding the extracellular domain of the human growth hormone (hGH) receptor from liver was cloned into a plasmid under control of the Escherichia coli alkaline phosphatase promoter and the heat-stable enterotoxin (StII) signal peptide sequence. Strains of E. coli expressing properly folded hGH binding protein were identified by blotting colonies with 125I-hGH. The E. coli strain capable of highest expression (KS330) secreted 10 to 20 mg/liter of culture of properly processed and folded hGH receptor fragment into the periplasmic space. The protein was purified to near homogeneity in 70 to 80% yield (in tens of milligram amounts) using ammonium sulfate precipitation, hGH affinity chromatography, and gel filtration. The unglycosylated extracellular domain of the hGH receptor has virtually identical binding properties compared to its natural glycosylated counterpart isolated from human serum, suggesting glycosylation is not important for binding of hGH. The extracellular binding domain codes for 7 cysteines, and we show that six of them form three disulfide bonds. Peptide mapping studies show these disulfides are paired sequentially to produce short loops (10-15 residues long) as follows: Cys38-Cys48, Cys83-Cys94, and Cys108-Cys122. Cys241 is unpaired, and mutagenic analysis shows that the extreme carboxyl end of the receptor fragment (including Cys241) is not essential for folding or binding of the protein to hGH. High level expression of this receptor binding domain and its homologs in E. coli will greatly facilitate their detailed biophysical and structural analysis.