Association of LHIα(B870) Polypeptide with Phospholipids During Insertion in the Photosynthetic Membrane of an LHII− Mutant of Rhodobacter capsulatus

Membranes from in vivo labeled cells of Rhodobacter capsulatus U43[pTX35] grown photosynthetically carried 60% of the [³²P]-Pi in the “heavy” fraction (HM) after sucrose gradient sedimentation. Metal-chelating chromatography of either “heavy” or “light” (LM) membrane fractions rendered similar Bchl-protein complex profiles after octyl-glucoside treatment, including most of the radioactivity in the same corresponding elution fraction (F II). Similar labeling distribution of pigment-protein complexes was obtained for membranes of dark-grown cells induced by lowering oxygen tension. Fractions derived from HM showed highly labeled LHIα, whereas the same complex from LM was essentially [³²P]-Pi-free, as revealed by SDS-PAGE followed by autoradiography. Phospholipid analysis showed a similar pattern for membranes isolated from cells photosynthetically or semiaerobically grown, being the most abundant: phosphatidylglycerol, phosphatidylethanolamine, cardiolipin, and phosphatidylcholine. Part of the phospholipids from HM comigrated with LHIα during SDS-PAGE and dissociated from the complexes only after solvent extraction and hydrophobic chromatography. However, a small amount remained always attached to LHIα, indicating an unusual strong interaction. These results suggest the existence of two operationally defined membrane regions carrying LHIα complexes differing in phosphorylation status and protein-phospholipid interaction. Received: 10 August 1996 / Accepted: 10 September 1996     

Gelled diet for screwworm (Diptera: Calliphoridae) mass production

A rearing system based on a diet gelled with Water-Lock G-400, a synthetic superabsorbent (poly(2-propenamide-co-2-propenoic acid, sodium salt)) (WL), was compared with the standard rearing system (liquid diet suspended in acetate fibers) for the mass production of screwworms, Cochliomyia hominivorax (Coquerel). The WL rearing system yielded 2% heavier pupae, 32% higher egg to pupa survival, and required 54% less diet and 88% less labor than the standard rearing system. Other advantages of the WL system include reduced susceptibility to suboptimal environmental conditions and labor practices and characteristics conducive to centralization and mechanization of rearing procedures.     

Synthesis and biological activity profiles of atrial natriuretic factor (ANF) analogs

Several analogs of the atrial natriuretic factor (ANF) were synthesized by the solid-phase method using the acetamidomethyl (Acm) group for sulfhydryl protection. The compounds were tested in a receptor binding assay using bovine adrenal zona glomerulosa cell membranes and in the rat diuresis/natriuresis assay. Substitution of tyrosine in position 116 of ANF(101-126) and of the analog [3-Mpr105]ANF(105-126)(3-Mpr = 3-mercaptopropionic acid) did not alter the biological activity profiles and, therefore, these two analogs in radioiodinated form will be useful for enzymatic degradation and clearance studies. Replacement of 3-mercaptopropionic acid with 2-mercaptopropionic acid in [3-Mpr105]ANF(105-126) resulted in an analog with very low potency in both assay systems, presumably as a consequence of the steric bulk and/or local conformational restriction produced by the methyl group attached to the alpha-carbon in position 105. The analog [3-Mpr105,Nva109]ANF(105-126)(Nva = norvaline) showed very low affinity in the receptor binding assay but displayed considerable diuretic/natriuretic activity. The obtained biological activity profiles suggest that in comparison with other ANF peptides the des-amino ANF(105-126) analogs may have a somewhat longer half-life in vivo, or alternatively, may indicate a more complex situation of ANF receptor or binding site heterogeneity.     

FBXO44 promotes DNA replication-coupled repetitive element silencing in cancer cells

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Structural basis for IL-12 and IL-23 receptor sharing reveals a gateway for shaping actions on T versus NK cells

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Cardiac myoglobin deficit has evolved repeatedly in teleost fishes

Myoglobin (Mb) is the classic vertebrate oxygen-binding protein present in aerobic striated muscles. It functions principally in oxygen delivery and provides muscle with its characteristic red colour. Members of the Antarctic icefish family (Channichthyidae) are widely thought to be extraordinary for lacking cardiac Mb expression, a fact that has been attributed to their low metabolic rate and unusual evolutionary history. Here, we report that cardiac Mb deficit, associated with pale heart colour, has evolved repeatedly during teleost evolution. This trait affects both gill- and air-breathing species from temperate to tropical habitats across a full range of salinities. Cardiac Mb deficit results from total pseudogenization in three-spined stickleback and is associated with a massive reduction in mRNA level in two species that evidently retain functional Mb. The results suggest that near or complete absence of Mb-assisted oxygen delivery to heart muscle is a common facet of teleost biodiversity, even affecting lineages with notable oxygen demands. We suggest that Mb deficit may affect how different teleost species deal with increased tissue oxygen demands arising under climate change.     

Vegetation fluctuation in mediterranean dune ponds in relation to rainfall variation and water extraction

Abstract. The structure of dune ponds hygrophytic vegetation has a spatial organisation in belts around the pond basin, closely related to water level and flooding regime. Doñana National Park has an important representation of temporal dune ponds, which are subjected to rainfall fluctuations and may be suffering the impact of water extraction from the neighbouring tourist resort. Permanent transects in a vegetation complex of five dune ponds have been monitored during a eight year period (1990-1997). This period was characterised by a number of dry years (annual rainfall around 300 mm), located between two wet cycles (800-900 mm). Transects were analysed in 1990 (wet period), 1994 (dry) and 1997 (wet) by hierarchical agglomera-tive clustering. During the dry period hygrophytic species showed regression, with a high mortality of some species like Ulex minor, while the xerophytic species advanced to lower areas. Seedlings of some xerophytic species colonised the dry surface of the pond basin. The lowering of the water table varied in the different ponds, ranging from 312 to 190 cm depending on topography and the distance to the pumping area. The new period of flooding during 1995-96 and 1996-97 cycles provided the opportunity for hygrophytic spe cies to re-establish themselves in their original places. This study suggest that changes in vegetation are caused by the interaction between weather conditions and human disturbance (water extractions). In our example man-made disturbance is more marked during the dry periods while wet periods tend to obscure the effects of water extractions. From a management perspective, long-term monitoring of water table and vegetation structure is revealed as a key procedure to the management of land-water ecotones on pressured areas and threatened habitats.