Ergatoid queens and intercastes in ants: Two distinct adult forms which look morphologically intermediate between workers and winged queens

Summary The term ergatogyne is used in ants to describe permanently-wingless female adults which are morphologically intermediate between workers and winged queens. This definition is ambiguous because there are two distinct categories of ergatogynes: ergatoid queens and intercastes. Both have an external appearance (ocelli and alitrunk structure) which combines traditional queen and worker characters, and thus can be confused if they both function as reproductives — however intercastes in most species cannot reproduce.Ergatoid queens have replaced winged queens in a substantial number of species. They are sometimes externally similar to conspecific workers, especially in various ponerine species which exhibit limited size dimorphism between castes. Ergatoid queens retain the specialized attributes of a reproductive caste, including larger ovaries, and they are always the functional egg-layers in a colony. In contrast, conspecific intercastes represent various graded stages in a series connecting workers and winged queens, and they occur together with the queens. These hybrid phenotypes result from deviations from the normal pattern of caste differentiation during larval development. Intercastes generally lack a spermatheca and have no reproductive function; however they can mate in a few leptothoracine ants, and then reproduce instead of winged queens in a proportion of colonies.     

Trace metals in the benthic habitat of the Maarsseveen Lakes system,The Netherlands

The cadmium, zinc, lead and copper concentrations in benthic invertebrates and sediment were determined during two consecutive winters in the Maarsseveen Lakes system. A sequential extraction procedure was applied to estimate the bioavailability of the trace metals in the sediment. Based on the trace metal analyses of organisms and sediment, it is concluded that the Maarsseveen Lakes system has background levels of cadmium, zinc, lead and copper. As the majority of metals was present in geochemically more stable sediment phases, the sequential extractions provided limited additional information on trace metal bioavailability.     

Phytoplankton primary production and nutrients in the Oosterschelde (The Netherlands) during the pre-barrier period 1980–1984

Phytoplankton primary production, nutrient concentrations and turbidity were monitored at three stations in the Oosterschelde during 1980–1984 as part of an ecosystem study.From comparisons of dissolved nutrient ratios with the nutrient requirements of phytoplankton, and of ambient nutrient concentrations with half-saturation constants for nutrient uptake by natural phytoplankton populations it was concluded that silicate was a limiting nutrient for diatoms after the spring bloom until the end of the summer. Dissolved inorganic nitrogen and phosphate were not considered to be limiting to phytoplankton growth.In general, the phytoplankton growing season started during the first fortnight of April and ended at the end of September. Column production in the whole Oosterschelde varied between 201 and 540 g C m^–2 yr^–1 and was, on average, 25% higher in the western part than in the eastern part. Basin production in the Oosterschelde varied between 120 and 466 g C m^–2 yr^–1 and was, on average, 55% higher in the western part than in the eastern part; this difference could be explained by differences in the ratio of euphotic depth to mean depth of the compartments.Estimated carbon-specific growth rates in the eastern part varied between < 0.1 and 3 d^–1 and in the western part between < 0.1 and 1 d^–1. This difference could be explained by the great differences in depth of the compartments. Carbon-specific growth rates are discussed in relation to phytoplankton loss rates. It is suggested that in the eastern part sedimentation must be an important sink for phytoplankton.Communication no. 473 of the Delta Institute for Hydrobiological Research, Yerseke, The Netherlands.     

Fluorescence investigation of the sex steroid binding protein of rabbit serum: steroid binding and subunit dissociation

The relationship between steroid binding and protein subunit interactions of rabbit sex steroid binding protein (rSBP) has been studied by steady-state and time-resolved fluorescence spectroscopy. The high-affinity (Ka approximately 10(8) M-1 at 4 degrees C), fluorescent estrogen d-1,3,5(10),6,8-estrapentaene-3,17 beta-diol [dihydroequilenin (DHE)] was used as a fluorescent probe of the steroid-binding site. Perturbation of the binding site with guanidinium chloride (Gdm.Cl) was monitored by changes in the steady-state fluorescence anisotropy of DHE as well as by changes in fluorescence quenching of DHE with acrylamide. The results of acrylamide quenching at 11 degrees C show that, while between 0 and 1 M Gdm.Cl the steroid-binding site is completely shielded from bulk solvent, there is decreased DHE binding. To study the subunit-subunit interactions, rSBP was covalently labeled with dansyl chloride in the presence of saturating 5 alpha-dihydrotestosterone (DHT), which yielded a dansyl-conjugated protein that retained full steroid-binding activity. The protein subunit perturbation was monitored by changes in the steady-state fluorescence anisotropy of the dansyl group. At 11 degrees C, the dansyl anisotropy perturbation, reflecting changes in global and segmental motions of the dimer protein, occurs at concentrations of Gdm.Cl above 1 M. The Gdm.Cl titration in the presence of steroids with equilibrium association constants less than 10(8) M-1 shows a plateau near 3 M Gdm.Cl at 11 degrees C; at this Gdm.Cl concentration, no DHE is bound. No plateau is observed at 21 degrees C. At higher Gdm.Cl concentrations, the dansyl fluorescence anisotropy decreases further and shows no steroid dependence. Recovery of steroid-binding activity (assayed by saturation binding with [3H]DHT), under renaturation conditions, is dependent on both steroid concentration and affinity. Both unlabeled and dansyl-labeled protein recovery the same amount of activity, and according to fluorescence anisotropy, dansyl-labeled rSBP re-forms a dimer upon dilution below 1 M or removal of Gdm.Cl. From the steroid requirement for recovery of steroid-binding activity, it appears that a conformational template is required for the dimeric protein to re-form a steroid-binding site with native-like properties.     

Isolation and characterization of active ribosomal subunits from human placenta.

We have developed a method for the large-scale isolation of active ribosomal subunits from human placenta. The technique involves incubating crude ribosomes for 15 min at 37 degrees C with 0.2 mM puromycin in 50 mM Tris-HCl buffer, pH 7.6, 500 mM KCl and 3 mM MgCl2 followed by centrifugation at 5 degrees C in a BXV zonal rotor using an equivolumetric sucrose gradient in the same buffer, upon which 80--90% of all ribosomes are dissociated into subunits. The purified subunits differ in their chemical composition, the 60-S particle containing no more than 36% protein whereas the 40-S subunit consists of 43% protein. In poly(U)-directed protein synthesis, tested in a completely homologous cell-free system, one recombined couple polymerizes at 37 degrees C 12 to 17 phenylalanine residues at an initial rate of 0.7 residues per minute. However, free 80-S ribosomes obtained by puromycin treatment of the crude ribosomes and reassociation of the subunits without prior isolation, have an even higher incorporating activity (20--25 mol phenylalanine/mol of ribosome). At least 55% of the subunits were estimated to actively participate in the polyphenylalanine synthesis.     

Observation and quantitation of metal-binding sites in the sex steroid-binding protein of human and rabbit sera using the luminescent probe terbium

The first direct evidence for specific metal-binding sites in pure human and pure rabbit sex steroid-binding protein (SBP) is obtained using the luminescent lanthanide terbium. Terbium, a probe for calcium sites in proteins, provided protection of the SBP steroid-binding activity in diluted human serum samples equivalent to that provided by calcium. Pure SBP, first treated with ethylenediaminetetraacetate, was dialyzed against buffer containing TbCl₃. After gel filtration to remove nonspecifically bound terbium, the protein was denatured in urea. The amount of protein-bound terbium was determined by luminescence enhancement of the lanthanide using the chelator dipicolinate, yielding four metal-binding sites per mole of dimer protein from both species.     

Efficacy of different types of aerobic exercise in fibromyalgia syndrome: a systematic review and meta-analysis of randomised controlled trials

Introduction  

The efficacy and the optimal type and volume of aerobic exercise (AE) in fibromyalgia syndrome (FMS) are not established. We therefore assessed the efficacy of different types and volumes of AE in FMS.