The C4-dicarboxylate transport system ofRhizobium meliloti and its role in nitrogen fixation during symbiosis with alfalfa (Medicago sativa)

TheRhizobium meliloti C₄-dicarboxylate transport (Dct) system is essential for an effective symbiosis with alfalfa plants. C₄-dicarboxylates are the major carbon source taken up by bacteroids. Genetic analysis of Dct^– mutant strains led to the isolation of thedct carrier genedctA and the regulatory genesdctB anddctD. The carrier genedctA is regulated in free-living cells by the alternative sigma factor RpoN and the two-component regulatory system DctB/D. In addition, DctA is involved in its own regulation, possibly by interacting with DctB. In bacteroids, besides the DctB/DctD system an additional symbiotic activator is thought to be involved indctA expression. Further regulation ofdctA in the free-living state is reflected by diauxic growth of rhizobia, with succinate being the preferred carbon source. The tight coupling of C₄-dicarboxylate transport and nitrogen fixation is revealed by a reduced level of C₄-dicarboxylate transport in nitrogenase negative bacteroids.     

La formule chromosomique deSorex minutus L. (Mammalia-Insectivora)

Summary The chromosome complement ofSorex minutus L. has been determined. The caryotype is characterized by a diploid number of 42 and by aNF (fundamental number) of 56. The sex-chromosomes are of theX−Y type usual in mammals. The origin and the evolution of the chromosome set ofS. minutus, S. unguiculatus, andS. araneus have been discussed.      

Microtubule inhibitors block the morphological changes induced inDrosophila blood cells by a parasitoid wasp factor

Summary The shape change ofDrosophila melanogaster blood cells (lamellocytes) from discoidal to bipolar that is caused by a factor from the female parasitoidLeptopilina heterotoma is blocked by the tubulin inhibitors vinblastine and vincristine in vitro. The actin inhibitor, cytochalasin B, causes arborization ofDrosophila lamellocytes and acts synergistically with the wasp factor to alter lamellocyte morphology. Lamellocyte arborization induced by cytochalasin B is blocked by simultaneous treatment with vinblastine. These observations indicate that the changes in lamellocyte shape induced by both the wasp factor and cytochalasin B require microtubule assembly.     

Protein O-GlcNAcylation regulates Drosophila growth through the insulin signaling pathway

Modification of nuclear and cytosolic proteins by O-linked N-acetylglucosamine (O-GlcNAcylation) is ubiquitous in cells. The in vivo function of the protein O-GlcNAcylation, however, is not well understood. Here, we manipulated the cellular O-GlcNAcylation level in Drosophila and found that it promotes developmental growth by enhancing insulin signaling. This increase in growth is due mainly to cell growth and not to cell proliferation. Our data suggest that the increase in the insulin signaling activity is mediated, at least in part, through O-GlcNAcylation of Akt. These results indicate that O-GlcNAcylation is one of the crucial mechanisms involved in control of insulin signaling during Drosophila development.     

Un nouveau système polymorphe robertsonien chez une nouvelle espèce de «Leggada» (Mus goundae Petter)

Summary A sample of 6 Leggada from N'Délé (Central African Republic) morphologically different from all these studied up to now, constitue a new species, which will be described by Dr F.Petter asMus goundae Petter. The caryological analysis reveals a new robertsonian polymorphical system. The diploïd numbers are 2N=16, 17, 18 or 19, whereas theN.F. is constant and equal to 30. The 3 first pairs of autosomes, constituted by SM or MC elements are identical in the 4 types, as well as pairs V (MC) and VI (AC) morphologically constant by all individuals. The robertsonian mechanisms, from which polymorphism originates, take place at pairs IV, VII and VIII. The fourth pair, while heterozygote by 2N=19, assembling one MC and two AC elements, is homozygote and MC by 2N=18, 17 and 16; pairs VII and VIII are both constituted by two AC in the cases of 19 and 18 chromosomes; to form caryotypes with 17 and 16 chromosomes these 2 pairs will fusion: by 2N=17 the mutation is heterozygote (1 MC and 2 AC) and it becomes homozygote by 2N=16 giving birth to 2 MC. The sexual chromosomes are from TR Type (X MC andY SM).From these observations arises the problem of low chromosome numbers (16–20) which shall be discussed in a further publication.     

Molecular characterization and expression of the antimicrobial peptide defensin from the housefly (Musca domestica)

A 430-bp cDNA encoding the insect antimicrobial peptide defensin was cloned from the housefly, and designated Musca domestica defensin (Mdde). The open reading frame of the cDNA encoded a 92-amino acid peptide with an N-terminal signal sequence followed by a propeptide that is processed by cleavage to a 40-amino acid mature peptide. Northern analysis and in situ hybridization identified the corresponding mRNA in the fat body of bacterially challenged houseflies and in the epidermis of the body wall of naive and challenged houseflies. The Gram-negative bacterium (Escherichia coli) is a strong inducer of the gene. By RT-PCR, Mdde mRNA was also detected in naive and challenged insects. These findings suggest that the defensin gene is constitutively expressed in the epidermis of the housefly body wall. The predicted mature form of Mdde was expressed as a recombinant peptide in E. coli and Pichia pastoris. The recombinant Mdde expressed in Pichia was active against Gram-positive and some Gram-negative bacteria. Received 20 June 2006; received after revision 3 October 2006; accepted 30 October 2006     

Host trail following by the guest antFormicoxenus provancheri

Formicoxenus provancheri, a guest ant ofMyrmica incompleta, is able to follow artificial trails made with the poison gland secretion of its host. The trail-following response is elicited at the same range of concentrations as for the host species. The performance ofFormicoxenus is enhanced by the presence of the host. The adaptive value of these phenomena is discussed.     

The clostridial mobilisable transposons

Mobilisable transposons are transposable genetic elements that also encode mobilisation functions but are not in themselves conjugative. They rely on coresident conjugative elements to facilitate their transfer to recipient cells. Clostridial mobilisable transposons include Tn4451 and Tn4452 from Clostridium perfringens, and Tn4453a and Tn4453b from Clostridium difficile, all of which are closely related, and Tn5398 from C. difficile. The Tn4451 group of elements encodes resistance to chloramphenicol and is unusual in that transposition is dependent upon a large resolvase protein rather than a more conventional transposase or integrase. This group of elements also encodes the mobilisation protein TnpZ that, by acting at the RS_A or oriT site located on the transposon, and in the presence of a coresident conjugative element, promotes the movement of the nonreplicating circular intermediate and of plasmids on which the transposon resides. The erythromycin resistance element Tn5398 is unique in that it encodes no readily identifiable transposition or mobilisation proteins. However, the element is still capable of intraspecific transfer between C. difficile isolates, by an unknown mechanism. The detailed analysis of these mobilisable clostridial elements provides evidence that the evolution and dissemination of antibiotic resistance genes is a complex process that may involve the interaction of genetic elements with very different properties. RID="*" ID="*"Corresponding author.     

Explaining Leibniz equivalence as difference of non-inertial appearances: Dis-solution of the Hole Argument and physical individuation of point-events

“The last remnant of physical objectivity of space–time” is disclosed in the case of a continuous family of spatially non-compact models of general relativity (GR). The physical individuation of point-events is furnished by the autonomous degrees of freedom of the gravitational field (viz., the Dirac observables) which represent—as it were—the ontic part of the metric field. The physical role of the epistemic part (viz. the gauge variables) is likewise clarified as embodying the unavoidable non-inertial aspects of GR. At the end the philosophical import of the Hole Argument is substantially weakened and in fact the Argument itself dissolved, while a specific four-dimensional holistic and structuralist view of space–time (called point-structuralism) emerges, including elements common to the tradition of both substantivalism and relationism. The observables of our models undergo real temporal change: this gives new evidence to the fact that statements like the frozen-time character of evolution, as other ontological claims about GR, are model dependent.     

Cytologie comparée des Muridae. L'origine des Ellobii

Summary (1) The present paper deals with the chromosomial cytology of 11 species and underspecies ofMuridae. (2) The diploïd number being the same (2N=42), there are striking differences between two species ofBandicota, B. indica showing about 20 big metacentric chromosomes which are lackingB. bengalensis. (3)Meriones blackleri is characterized by 72 chromosomes, the species previously described possessing either 44 or 60 elements. (4) The study ofPhenacomys ungava confirms the view that 56 (54) is the primitive number in theMicroti. There is an interesting parallelism between the morphological and the cytological data. (5) A missing link betweenMicroti andEllobii has been found inMicrotus oregoni which possesses 17 chromosomes, its digamety belonging to the typeX-O, X-X. (6) Owing to the fact thatM. oregoni is more fossorial than the otherMicrotus, it is a morphological intermediate betweenMicroti andEllobii. (7) The genusChilotus (Baird) is also fully valid.     

Systematics and evolution of holarctic Pierinae (Lepidoptera). An enzyme electrophoretic approach

Summary Enzyme electrophoretic data show a remarkably high degree of genetic similarity within the European group ofnapi s.l. whereas genetic differences exist at several loci between the European and the North American taxa ofnapi s.l. It is concluded that the European taxa did not differentiate to the species level and form a phylogenetically young group. The North American taxa included in this study are specifically distinct from Europeannapi and separated much earlier. Within these North American taxamarginalis, oleracea andvirginiensis did undergo speciation. The data show a splitting of the genusPieris into three species groups, each genetically differentiated to the same level. The splitting ofPieris into two genera, as suggested by earlier investigators, is not supported here.     

Rote augen als mutante beiCulex pipiens L

Summary A red-eyed sex-linked mutantra ofCulex pipiens is discussed in relation to a recently published mutantr. A common origin might be postulated. The mutantra is characterized by a fluorescence substance not present in the wild type.     

Cryo-bioorganic chemistry: freezing effect on stereoselection of l- and dl-leucine cooligomerization in aqueous solution

The chirality of l-/dl-leucine (50–50%) cooligomerization was investigated in liquid and frozen aqueous solutions. Cooligomerization was carried out by carbonyldiimidazole activation without initiator at an ambient (+22°C) and frozen (−18°C) temperature, respectively. The separated samples obtained after different time intervals of treatment were completely hydrolyzed (HCl) and the diastereomeric l- and d-leucine derivates of Marfey's reagent (1-fluoro-2,4-dinitrophenyl-5-l-alanine amide) were then traced and evaluated by RP-HPLC analysis. After 9 days of oligomerization, the l-Leu content was slightly enhanced in the liquid (57%) and somewhat more enhanced in the frozen (64%) samples. After 17 days, however, the l-Leu content had decreased in the liquid (53%) and frozen (56%) conditions. These l-enantiomer amplifications indicate that an l-antipode is preferentially incorporated into the α-helical turn of the oligomer in the earlier stage of cooligomerization, while, later, the d-antipode is also incorporated. The role of ice in the improved stereoselection is discussed. This is the first recorded example of the effect of freezing on stereoselection. Received 27 October 2000; revised 11 December 2000; accepted 4 January 2000     

Structure and assembly of the 20S proteasome

The barrel-shaped 20S proteasome is one of the two components of a larger 26S particle, the multicatalytic 2000-kDa protease complex. The proteolytic sites are located in the inner chamber of the 20S particle and are only accessible via narrow entrances. This paper reviews the current knowledge concerning proteasome formation, proteolytic activities, structural aspects and assembly. Eukaryotic proteasomes are made up by four rings each of which contains seven different subunits occurring at fixed positions. While the outer rings contain α-type subunits, the inner ones comprise β-type subunits. The current assembly model for eukaryotic 20S proteasomes is based upon the detection of 13S and 16S intermediates, respectively, in addition to previous findings with archaebacterial and eubacterial proteasome assembly. The available data suggest a cooperative assembly of the α-type and β-type subunits into half proteasome-like complexes followed by dimerization into proteasomes. During or after dimerization of half proteasomes, the β-type subunits are processed. The prosequence of the β-type subunits is essential for the assembly process and prevents protease activity of immature proteasomes.     

Sonnenflecken und ihre terrestrischen Wirkungen

Summary After a discussion of the 11-year solar-cycle as regarded from the standpoint of the eruption-hypothesis, which offers a possibility to predict the solar activity for several years and after a review of the magnetic properties of the sun and the sunspots, the paper deals with the new theories of the spots and the solar-cycle as suggested byAlfvén andWalén.The terrestrial effects of the phenomena associated with the solar cycle are classified into 4 groups: effects produced by a) a wave radiationW _k emitted continuously by the sun, b) a wave radiationW _e emitted from the chromospheric eruptions, c) a particle radiationP _k emitted by the so-called M-regions, and d) a particle radiationP _e ejected from the eruptions. The connection between the solar eruptions and the radiationsP _e ,W _e is a well established fact; on the other hand the radiationsW _k ,P _k could be connected by the author with the solar corona and the stationary solar prominences respectively.To account for the intensity of theW _k -radiation a temperature of the solar corona of one million degree is required in agreement with the observed temperature. The heating of the corona occurs in the electric field around an increasing sunspot. As in the corona the mean free path amounts to several kilometers, particles may be accelerated up to 1000 eV, so far the conditionh=0 is fulfilled. Generally speaking acceleration is possible only in such regions whereh andh are not perpendicular to each other.     

Über die Membransubstanzen vonChlorochytridion tuberculatum W. Vischer

Summary The membrane ofChlorochytridion tuberculatum (nov. gen., nov. spec.) W. Vischer is analyzed by X-ray spectrography. Cellulose, quartz, and calcite are detected. It is remarkable that quartz, which does not crystallize under physiological conditionsin vitro, is formed in the cell wall ofChlorochytridion.     

Multiple phosphoglucomutase alleles in two species ofMansonia mosquito

Summary Multiple phosphoglucomutase (E.C.2.7.5.1) alleles are found in the mosquitoesMansonia crassipes andM. uniformis. The present study reveals 4Pgm alleles, of whichPgm ^B andPgm ^C are common to both species whilePgm ^A is present only inM. crassipes andPgm ^D only inM. uniformis. The frequencies in both species accord well with Hardy-Weinberg expectations. The most frequent allele is that controlling a phenotype with an intermediate electrophoretic mobility, viz.Pgm ^B inM. crassipes andPgm ^C inM. uniformis.This work is supported in part by a University of Malaya research grant to the senior author.     

Identification of chicken lysozyme <Emphasis Type="Italic">g</Emphasis>2 and its expression in the intestine

Lysozyme is an important component of the innate immune system, protecting the gastrointestinal tract from infection. The aim of the present study was to determine if lysozyme is expressed in the chicken (Gallus gallus) intestine and to characterise the molecular forms expressed. Immunohistochemical staining localised lysozyme to epithelial cells of the villous epithelium along the length of the small intestine. There was no evidence for lysozyme expression in crypt epithelium and no evidence for Paneth cells. Immunoblots of chicken intestinal protein revealed three proteins: a 14-kDa band consistent with lysozyme c, and two additional bands of approximately 21 and 23 kDa, the latter consistent with lysozyme g. RT-PCR analyses confirmed that lysozyme c mRNA is expressed in 4-day, but not older chicken intestine and lysozyme g in 4- to 35-day chicken intestine. A novel chicken lysozyme g2 gene was identified by in silico analyses and mRNA for this lysozyme g2 was identified in the intestine from chickens of all ages. Chicken lysozyme g2 shows similarity with fish lysozyme g, including the absence of a signal peptide and cysteines involved in disulphide bond formation of the mammalian and bird lysozyme g proteins. Analyses using SecretomeP predict that chicken lysozyme g2 may be secreted by the non-classical secretory pathway. We conclude that lysozyme is expressed in the chicken small intestine by villous enterocytes. Lysozyme c, lysozyme g and g2 may fulfil complimentary roles in protecting the intestine.Received 4 August 2004; received after revision 1 September 2004; accepted 7 September 2004     

RTA2 is involved in calcineurin-mediated azole resistance and sphingoid long-chain base release in Candida albicans

The calcineurin pathway has been reported to be essential for the development of azole resistance in Candida albicans. The depletion or ectopic over-expression of RTA2 increased or decreased susceptibility of C. albicans to azoles, respectively. CaCl₂- induced activation of the calcineurin pathway in wildtype C. albicans promoted resistance to azoles, while the Ca ²⁺ chelator (EGTA), calcineurin inhibitors (FK506 and cyclosporin A) and the deletion of RTA2 blocked the resistance-promoting effects of CaCl₂. Furthermore, we found that RTA2 was up-regulated in a calcineurin-dependent manner. The depletion of RTA2 also made the cell membrane of C. albicans liable to be destroyed by azoles and RTA2 over-expression attenuated the destroying effects. Finally, the disruption of RTA2 caused an increased accumulation of dihydrosphingosine (DHS), one of the two sphingolipid long-chain bases, by decreasing release of DHS. In conclusion, our findings suggest that RTA2 is involved in calcineurin-mediated azole resistance and sphingoid long-chain base release in C. albicans. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Received 14 July 2008; received after revision 29 August 2008; accepted 16 September 2008     

John Hunter and his approach to pathology

Given the old conception of the relation greater than, the proposition that the whole is greater than the part is an immediate consequence. But being greater in this sense is not incompatible with being equal in the sense of one-one correspondence. Some who failed to recognize this formulated invalid arguments against the possibility of infinite quantities. Others who did realize that the relations of equal and greater when so defined are compatible, concluded that such relations are not appropriately taken as quantitative relations, at least, not in general. If suitable quantitative relations were to be defined, there was a possibility of retaining either the traditional definition of greater and finding another concept of equality, or of retaining the concept of equality as one-one correspondence and defining greater than so that it is incompatible with equality in this sense. The former alternative was implicitly taken by Bolzano, who never succeeded in defining suitable quantitative relations. The latter alternative was taken by Cantor, and is the basis of his great success in constructing a mathematical theory of the transfinite.