Responses of visual interneurons in the fly optic lobe during stimulation by motion in depth

Summary A high-order wide-field neuron in the optic lobe of the fly,Phormia terraenovae (Calliphoridae), has been investigated by stimulation with simple or multiple black stripes on a white background moving sinusoidally towards and away from the head. The variation in spike frequency in correlation with the optical stimulation provides evidence that the unit detects angular velocity as well as more complex features of the stimulus. It responds preferentially to movement towards the head. Spike frequency turned out to be a two-valued function of relative angular velocity across the eye. A simple formula predicts the highly reliable responses to visual stimuli in different parts of the visual field.The author wants to thank Professor G. A. Horridge for his valuable support and clarifying discussions and to Dr. M. Srinivasan for his comments. The project has been supported by grants from the Swedish Council for Natural Science Research.     

Ultrastructural demonstration of cartilage acid glycosaminoglycans

Synopsis A method for the demonstration of cartilage acid glycosaminoglycans by light and electron microscopy is described. Rabbit ear cartilage was fixed in cacodylate buffered 2.5% methanol-free formaldehyde with 0.001 M Ruthenium Red andp-chloromercuribenzoate (PCMB). Dehydration was carried out in ethylene glycol followed by embedding in the water-soluble glycol methacrylate (GMA). In some experiments unfixed cartilage was rapidly dehydrated. Sections, 1 thick, and ultrathin sections from the same blocks were stained with 0.001 M Ruthenium Red. Semi-thin sections from cartilage fixed without heavy metal additives were, in addition, stained with the acidophilic fluorochrome Berberine sulphate. It was found that Ruthenium Red intensely stained the same pericellular zone that stained metachromatically with Toluidine Blue or fluoresced after staining with Berberine sulphate. Prior treatment with 0.05% cetylpyridinium chloride entirely blocked the three reactions. Previous digestion with 0.2 mg hyaluronidase/ml for 30 min at 37°C led to the abolition of the fluorescence reaction with Berberine sulphate. It is concluded that Ruthenium Red selectively stains cartilage acid glycosaminoglycans. With the electron microscope the pericellular zones were found to be built up of a three-dimensional branched meshwork of fibrils covered with a mantle of electron-dense material, presumably acid glycosaminoglycans bound to Ruthenium Red.     

Identification of the para-isomer of tyramine in rat brain

By means of thin layer chromatography and mass spectrometry of dansylated tissue extracts tyramine has been identified in different regions of the rat CNS. The isomer present is the $\text{para}$-tyramine; no $\text{ortho}$- or $\text{meta}$-tyramine could be found.     

Specific binding of lactoferrin to Aeromonas hydrophila.

The interaction of lactoferrin (Lf) with Aeromonas hydrophila (n = 28) was tested in a 125I-labeled protein-binding assay. The mean per cent binding values for human Lf (HLf) and bovine Lf (BLf) were 13.4 +/- 2.0 (SEM), and 17.5 +/- 2.7 (SEM), respectively. The Lf binding was characterized in type strain A. hydrophila subsp. hydrophila CCUG 14551. The HLf and BLf binding reached a complete saturation within 2 h. Unlabeled HLf and BLf displaced 125I-HLf binding in a dose-dependent manner, and more effectively by the heterologous (1 microgram for 50% inhibition) than the homologous (10 micrograms for 50% inhibition) ligand. Apo- and holo-forms of HLf and BLf both inhibited more than 80%, while mucin caused approx. 50% inhibition of the HLf binding. Various other proteins (including transferrin) or carbohydrates did not block the binding. Two HLf-binding proteins with an estimated molecular masses of 40 kDa and 30 kDa were identified in a boiled-cell-envelope preparation, while the unboiled cell envelope demonstrated a short-ladder pattern at the top of the separating gel and a second band at approx. 60 kDa position. These data establish a specific interaction of Lf and the Lf-binding proteins seem to be porins in A. hydrophila.     

Temporal variation in male traits, nesting aggregations and mating success in the peacock blenny

At the beginning of the breeding season male Salaria pavo that have eggs in their nests are larger, have more developed anal glands and less intense eye-spots and are located in breeding aggregations. These differences cease to occur from the peak of the breeding season (June—July) onwards. Two scenarios are presented that may explain these results: (1) smaller and younger males may begin to breed later devoting part of the warm season to growth; (2) females may cease to be selective as the nesting space begins to be saturated with eggs. These results raise one methodological and one conceptual question. The search for correlates of male reproductive success must cover different phases of the breeding season to capture the overall dynamics of the processes involved. The operational sex ratio for cavity-spawning fishes should take into account the availability of spawning sites rather than just counting the sexually mature members of each sex.     

Human-induced Trophic Cascades and Ecological Regime Shifts in the Baltic Sea

Abstract The ecosystems of coastal and enclosed seas are under increasing anthropogenic pressure worldwide, with Chesapeake Bay, the Gulf of Mexico and the Black and Baltic Seas as well known examples. We use an ecosystem model (Ecopath with Ecosim, EwE) to show that reduced top-down control (seal predation) and increased bottom-up forcing (eutrophication) can largely explain the historical dynamics of the main fish stocks (cod, herring and sprat) in the Baltic Sea between 1900 and 1980. Based on these results and the historical fish stock development we identify two major ecological transitions. A shift from seal to cod domination was caused by a virtual elimination of marine mammals followed by a shift from an oligotrophic to a eutrophic state. A third shift from cod to clupeid domination in the late 1980s has previously been explained by overfishing of cod and climatic changes. We propose that the shift from an oligotrophic to a eutrophic state represents a true regime shift with a stabilizing mechanism for a hysteresis phenomenon. There are also mechanisms that could stabilize the shift from a cod to clupeid dominated ecosystem, but there are no indications that the ecosystem has been pushed that far yet. We argue that the shifts in the Baltic Sea are a consequence of human impacts, although variations in climate may have influenced their timing, magnitude and persistence. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Deformed wing virus associated with <Emphasis Type="Italic">Tropilaelaps mercedesae</Emphasis> infesting European honey bees (<Emphasis Type="Italic">Apis mellifera</Emphasis>)

Mites in the genus Tropilaelaps (Acari: Laelapidae) are ectoparasites of the brood of honey bees (Apis spp.). Different Tropilaelaps subspecies were originally described from Apis dorsata, but a host switch occurred to the Western honey bee, Apis mellifera, for which infestations can rapidly lead to colony death. Tropilaelaps is hence considered more dangerous to A. mellifera than the parasitic mite Varroa destructor. Honey bees are also infected by many different viruses, some of them associated with and vectored by V. destructor. In recent years, deformed wing virus (DWV) has become the most prevalent virus infection in honey bees associated with V. destructor. DWV is distributed world-wide, and found wherever the Varroa mite is found, although low levels of the virus can also be found in Varroa free colonies. The Varroa mite transmits viral particles when feeding on the haemolymph of pupae or adult bees. Both the Tropilaelaps mite and the Varroa mite feed on honey bee brood, but no observations of DWV in Tropilaelaps have so far been reported. In this study, quantitative real-time RT-PCR was used to show the presence of DWV in infested brood and Tropilaelaps mercedesae mites collected in China, and to demonstrate a close quantitative association between mite-infested pupae of A. mellifera and DWV infections. Phylogenetic analysis of the DWV sequences recovered from matching pupae and mites revealed considerable DWV sequence heterogeneity and polymorphism. These polymorphisms appeared to be associated with the individual brood cell, rather than with a particular host.     

Synthesis and biodistribution of 211At-labeled,biotinylated, and charge-modified poly-L-lysine: evaluation for use as an effector molecule in pretargeted intraperitoneal tumor therapy

Poly-L-lysine (7, 21, and 204 kDa) has been evaluated as an effector carrier for use in pretargeted intraperitoneal tumor therapy. For the synthesis, the epsilon-amino groups on the poly-L-lysine were modified in three steps utilizing conjugate biotinylation with biotin amidocaproate N-hydroxysuccinimide ester (BANHS), conjugate radiolabeling with (211)At using the intermediate reagent N-succinimidyl 3-(trimethylstannyl)benzoate (m-MeATE), and charge modification using succinic anhydride, resulting in an increase in the molecular weight of approximately 80% of the final product. The labeling of the m-MeATE reagent and subsequent conjugation of the polymer were highly efficient with overall radiochemical yields in the range of 60-70%. The in vitro avidin binding ability of the modified polymer was almost complete (90-95%), as determined by binding to avidin beads using a convenient filter tube assay. Following intraperitoneal (ip) injection in athymic mice, the 13 kDa polymer product was cleared mainly via the kidneys with fast kinetics (biological half-live T(b) approximately 2 h) and with low whole-body retention. The clearance of the 38 kDa polymer was distributed between kidneys and liver, and the 363 kDa polymer was mainly sequestered by the liver with a T(b) of 8 h. Increased tissue uptake in the thyroid, lungs, stomach, and spleen following the distribution of the large effector molecules (38 and 363 kDa) suggests that degradation of the polymers by the liver may release some of the label as free astatine/astatide.