Life‐history strategies of the rock hind grouper Epinephelus adscensionis at Ascension Island

Epinephelus adscensionis sampled from Ascension Island, South Atlantic Ocean, exhibits distinct life‐history traits, including larger maximum size and size at sexual maturity than previous studies have demonstrated for this species in other locations. Otolith analysis yielded a maximum estimated age of 25 years, with calculated von Bertalanffy growth parameters of: L_∞ = 55·14, K = 0·19, t₀ = ?0·88. Monthly gonad staging and analysis of gonad‐somatic index (I_G) provide evidence for spawning from July to November with an I_G peak in August (austral winter), during which time somatic growth is also suppressed. Observed patterns of sexual development were supportive of protogyny, although further work is needed to confirm this. Mean size at sexual maturity for females was 28·9 cm total length (L_T; 95% C.I. 27·1–30·7 cm) and no females were found >12 years and 48·0 cm L_T, whereas all confirmed males sampled were mature, >35·1 cm L_T with an age range from 3 to 18 years. The modelled size at which 50% of individuals were male was 41·8 cm (95% C.I. 40·4–43·2 cm). As far as is known, this study represents the first comprehensive investigation into the growth and reproduction of E. adscensionis at its type locality of Ascension Island and suggests that the population may be affected less by fisheries than elsewhere in its range. Nevertheless, improved regulation of the recreational fishery and sustained monitoring of abundance, length frequencies and life‐history parameters are needed to inform long‐term management measures, which could include the creation of marine reserves, size or temporal catch limits and stricter export controls.     

Humerus development in moles (Talpidae,Mammalia)

The humerus of fossorial moles has a highly derived anatomy, reflecting the ecological specialization of these animals for digging. It is short and broad, with enlarged muscle attachment sites and pronounced articulations compared to non‐fossorial sister taxa and other mammals. Both condyles are rotated in opposite directions, resulting in a torsion which is unique among eutherian mammals. The development of this exceptional bone was studied in embryonic stages of the fossorial Iberian mole (Talpa occidentalis) from mesenchymal condensation to incipient ossification based on histological serial sections using 3D reconstruction methods. For comparison, embryonic stages of the semi‐fossorial Japanese shrew mole (Urotrichus talpoides) as well as a sister taxon of moles, the terrestrial North American least shrew (Cryptotis parva), were studied. Results show that the humerus of Talpa already shows its derived anatomy with broadened muscle attachment sites and distinct articulations at early cartilaginous stages, when ossification has just started in the mid‐diaphyseal region. The torsion takes place simultaneously with the medial rotation of the forelimbs. The supracondylar foramen is closed in all studied Talpa embryos, but patent in Cryptotis and Urotrichus. This is an example of developmental penetrance, suggesting that variation of adult elements can be found at early stages as well.     

Stromal fibroblasts present in invasive human breast carcinomas promote tumor growth and angiogenesis through elevated SDF-1/CXCL12 secretion

Fibroblasts often constitute the majority of the stromal cells within a breast carcinoma, yet the functional contributions of these cells to tumorigenesis are poorly understood. Using a coimplantation tumor xenograft model, we demonstrate that carcinoma-associated fibroblasts (CAFs) extracted from human breast carcinomas promote the growth of admixed breast carcinoma cells significantly more than do normal mammary fibroblasts derived from the same patients. The CAFs, which exhibit the traits of myofibroblasts, play a central role in promoting the growth of tumor cells through their ability to secrete stromal cell-derived factor 1 (SDF-1); CAFs promote angiogenesis by recruiting endothelial progenitor cells (EPCs) into carcinomas, an effect mediated in part by SDF-1. CAF-secreted SDF-1 also stimulates tumor growth directly, acting through the cognate receptor, CXCR4, which is expressed by carcinoma cells. Our findings indicate that fibroblasts within invasive breast carcinomas contribute to tumor promotion in large part through the secretion of SDF-1.     

The nitrosative stress response of Staphylococcus aureus is required for resistance to innate immunity

Staphylococcus aureus is a highly virulent human pathogen with an extensive array of strategies to subvert the innate immune response. An important aspect of innate immunity is the production of the nitrogen monoxide radical (Nitric Oxide, NO.). Here we describe an adaptive response to nitrosative stress that allows S. aureus to replicate at high concentrations of NO.. Microarray analysis revealed 84 staphylococcal genes with significantly altered expression following NO. exposure. Of these, 30 are involved with iron-homeostasis, potentially under the control of the Fur regulator. Another seven induced genes are involved in hypoxic/fermentative metabolism, including the flavohaemoprotein, Hmp. The SrrAB two-component system has been shown to regulate the expression of many of the NO.-induced metabolic genes. Indeed, inactivation of hmp, srrAB and fur resulted in heightened NO. sensitivity. Hmp was responsible for c. 90% of measurable staphylococcal NO. consumption and therefore critical for efficient NO. detoxification. While SrrAB was required for maximal hmp expression, srrAB mutants still exhibited significant NO. scavenging and NO.-dependent induction of hmp. Yet S. aureus lacking SrrAB were more sensitive to nitrosative stress than hmp mutants, indicating that the contribution of SrrAB to NO. resistance extends beyond the regulation of hmp expression. Both Hmp and SrrAB were required for full virulence in a murine sepsis model, however, only the attenuation of the hmp mutant was restored by the abrogation of host NO. production. Thus, the S. aureus Hmp protein has evolved to serve as an iNOS-dependent virulence determinant.     

Expression and characterization of the assimilatory NADH-nitrite reductase from the phototrophic bacterium Rhodobacter capsulatus E1F1

A nas gene region from Rhodobacter capsulatus E1F1 containing the putative nasB gene for nitrite reductase was previously cloned. The recombinant His₆-NasB protein overproduced in E. coli showed nitrite reductase activity in vitro with both reduced methyl viologen and NADH as electron donors. The apparent K _m values for nitrite and NADH were 0.5 mM and 20 μM, respectively, at the pH and temperature optima (pH 9 and 30°C). The optical spectrum showed features that indicate the presence of FAD, iron-sulfur cluster and siroheme as prosthetic groups, and nitrite reductase activity was inhibited by sulfide and iron reagents. These results indicate that the phototrophic bacterium R. capsulatus E1F1 possesses an assimilatory NADH-nitrite reductase similar to that described in non-phototrophic organisms.     

Partial sequence analysis of Xenopus alpha- and beta-globin mRNA as determined from recombinant DNA plasmids

Recombinant plasmids containing Xenopus globin mRNA sequences have been constructed using the mRNA:cDNA hybrid conditions of Zain et al. (1979, Cell16, 851–861). The partial nucleotide sequence of two of these recombinants has been determined. They have been identified as containing α- and β-globin-like sequences by homology to other amphibian globin proteins. The nucleotide sequence of these recombinants permits the comparison of conserved regions in both the coding and 3′ nontranslated regions of Xenopus globin mRNAs with the known sequences of other eukaryotic globin proteins and mRNAs. Among the features which have been conserved though evolution is the sequence AAUAAA close to the 3′ terminus of the nontranslated region. Extensive regions of homology occur between the 3′ nontranslated regions of Xenopus α- and β-globin mRNA.     

Nitric oxide storage and transport in cells are mediated by glutathione S-transferase P1-1 and multidrug resistance protein 1 via dinitrosyl iron complexes

Nitrogen monoxide (NO) plays a role in the cytotoxic mechanisms of activated macrophages against tumor cells by inducing iron release. We showed that NO-mediated iron efflux from cells required glutathione (GSH) (Watts, R. N., and Richardson, D. R. (2001) J. Biol. Chem. 276, 4724-4732) and that the GSH-conjugate transporter, multidrug resistance-associated protein 1 (MRP1), mediates this release potentially as a dinitrosyl-dithiol iron complex (DNIC; Watts, R. N., Hawkins, C., Ponka, P., and Richardson, D. R. (2006) Proc. Natl. Acad. Sci. U.S.A. 103, 7670-7675). Recently, glutathione S-transferase P1-1 (GST P1-1) was shown to bind DNICs as dinitrosyl-diglutathionyl iron complexes. Considering this and that GSTs and MRP1 form an integrated detoxification unit with chemotherapeutics, we assessed whether these proteins coordinately regulate storage and transport of DNICs as long lived NO intermediates. Cells transfected with GSTP1 (but not GSTA1 or GSTM1) significantly decreased NO-mediated 59Fe release from cells. This NO-mediated 59Fe efflux and the effect of GST P1-1 on preventing this were observed with NO-generating agents and also in cells transfected with inducible nitric oxide synthase. Notably, 59Fe accumulated in cells within GST P1-1-containing fractions, indicating an alteration in intracellular 59Fe distribution. Furthermore, electron paramagnetic resonance studies showed that MCF7-VP cells transfected with GSTP1 contain significantly greater levels of a unique DNIC signal. These investigations indicate that GST P1-1 acts to sequester NO as DNICs, reducing their transport out of the cell by MRP1. Cell proliferation studies demonstrated the importance of the combined effect of GST P1-1 and MRP1 in protecting cells from the cytotoxic effects of NO. Thus, the DNIC storage function of GST P1-1 and ability of MRP1 to efflux DNICs are vital in protection against NO cytotoxicity.