Geschlechtsspezifische Unterschiede beim Nahrungserwerb des Fichtenkreuzschnabels (Loxia curvirostra)

Summary By recording the rate of glancing (i. e. looking up), the number of seeds taken by a crossbill per unit time from a larch cone (Larix X eurolepis) was evaluated. Female crossbills took more seeds per unit time from the cones than males do. Because of similar bill (and body) sizes the sexual difference could be explained in the following ways: a) during the breeding season the females need more energy for egg production than males do for spermatogenesis; b) females are more vigilant than males.     

Filter mesh size and food particle uptake by Daphnia

Food size selection of four Daphnia, species (D. magna, D. hyalina, D. galeata, D. pulicaria) was investigated using spherical plastic beads as artificial food and with small bacteria. The size of the particles ranged from 0.1 to 35 m with special emphasis to the particle diameters between 0.1 and 1 m. In one set of experiments a mixture of differently sized particles was offered as food suspension and the selectivity of filtering was determined by comparing the size spectrum of the particles found in the gut contents with the spectrum in the food suspension. In a second series of experiments suspensions of uniformly sized particles were offered to single animals and their feeding activity was observed directly. In both types of experiments the mesh sizes of the filtering apparatus of the respective animals studied were measured after the experiments by, scanning electron microscopy. The mean sizes of the filter meshes were about 0.4–0.7 m. In all experiments the size of the particles found in the gut or those which caused high feeding activities were larger than the smallest mesh sizes of the filters. As a consequence simple mechanical sieving provides a sufficient explanation for the mechanism of particle retention of the filtering process in Daphnia. D. magna was found to feed with high efficiency on suspended freshwater bacteria, the residual species investigated showed low filtering efficiencies when bacteria were offered as food.The present study was supported by Deutscher Akademischer Austauschdients     

Peptidoglycans as promoters of slow-wave sleep. II. Somnogenic and pyrogenic activities of some naturally occurring muramyl peptides; correlations with mass spectrometric structure determination

The structures of components of the sleep-promoting material purified from human urine were established by fast atom bombardment-mass spectrometry, as reported in the accompanying paper (Martin, S. A., Karnovsky, M. L., Krueger, J. M., Pappenheimer, J. R., and Biemann, K. (1984) J. Biol. Chem. 259, 12652-12658). We report here that two substances isolated from that preparation, viz. N-acetylglucosaminyl-1,6 -anhydro-N-acetylmuramyl-Ala-gamma-Glu-diaminopimelyl-Ala) and that compound lacking the terminal alanine, are active as somnogens. Cerebro-intraventricular administration of 1 pmol of the glycotetrapeptide was sufficient to induce prolonged excess sleep in rabbits. A similar substance obtained from Brevibacterium divaricatum in which the free carboxyls of the glutamic and diaminopimelic moieties, indicated above, were amidated (N-acetylglucosaminyl-1,6-anhydro-N-anhydromura-myl-Ala-iso- Gln- epsilon-amido-diaminopimelyl -Ala-Ala) was not active as a promoter of slow-wave sleep. Deamidation of this peptide to a mixture of the free dicarboxylic forms produced a somnogenic substance. Our findings show that in addition to the muramyl form of peptidoglycan monomers, the anhydro muramyl form, with no reducing end, is compatible with somnogenic activity. Furthermore, the data obtained with a natural product amplify our earlier observations with smaller synthetic molecules of the importance of amidation/deamidation in the structure-activity relationships of muramyl peptides.     

Human Ile-Ser-bradykinin, identical with rat T-kinin, is a major permeability factor in ovarian carcinoma ascites

Ascites from patients with metastatic ovarian carcinoma contains high amounts of an activity that increases vascular permeability, as easily detected by a rat skin test. Ascites was fractionated by gel permeation and reversed-phase high-performance liquid chromatographies. The fractions were analysed for permeability-increasing activity. In this way a peptide was isolated and identified as Ile-Ser-bradykinin by sequence and amino-acid analyses. It is identical with T-kinin which has previously been detected as a product of an acute-phase protein, T-kininogen, in rats but never in human material. The so far identified human kininogens, i.e. high- and low-molecular mass kininogens, can only release Met-Lys-bradykinin or its degradations products, as Ile-Ser-bradykinin is not a part of their structure. However, the present results provide evidence that the permeability factor Ile-Ser-bradykinin under certain conditions can be produced in considerable amounts also by human tissues.     

Rate of Supply of Sugar Solution and Behaviour of Collector Wasps (Paravespula germanica)

The rate of supply of sucrose solution at an artificial food source was varied by means of a pump, while the concentration of the solution and the temperature at the food source were kept constant. The behaviour of the collector wasps was found to change in correlation with the supply rate, in several respects. As rate of supply increases

• a) the duration of sojourn at the food source decreases;
• b) the volume of solution removed per h increases;
• c) the number of single visits during a sojourn and per h decreases;
• d) the duration of single visits increases, except that at extremely high supply rates the single visits become shorter.

The waiting time (Saugwartezeit) does not depend on supply rate. Comparison of these wasp data with related observations of honeybees (Apis mellifera) supports inferences regarding the motivation of collector wasps and, in view of the frequency of their single visits, about their suitability as potential pollinators of the flowers from which they collect.     

Conductimetric assessment of the biomass content in suspensions of immobilised (gel-entrapped) microorganisms

Summary The problem of obtaining a rapid estimate of the microbial content of an immobilised cell suspension is addressed. The low-frequency conductivity of free-living cell suspensions of Clostridium pasteurianum is lower than that of the medium in which they are suspended, by an amount conforming to the Bruggeman relation. The conductivity of the cell wall makes a negligible contribution to the measured conductivity under the conditions used. Calcium alginate beads (lacking microbial cells) lower the conductivity of a solution with which they have been equilibrated by an extent which is a function of the concentration of alginate gel used in forming the beads. When this is taken into account, the ratio of the conductivity of a suspension of gel-immobilised cells to that of the suspending medium can be used to give a rapid and convenient assessment of the amount of microbial biomass present.     

Neural coding of difference frequencies in the midbrain of the electric fishEigenmannia: Reading the sense of rotation in an amplitude-phase plane

Eigenmannia is able to discriminate the sign of the difference, Df, between the frequency of a neighbor's electric organ discharge (EOD) and that of its own EOD. This discrimination can be demonstrated at the level of individual neurons of the midbrain. Intracellular and extracellular recordings of such sign-selective cells revealed the following: Units preferring positive Dfs and units preferring negative Dfs were found with equal frequency. The degree of selectivity was also similar for these two classes of neurons. All sign-selective units were sensitive to the magnitude of the frequency difference, i.e. the beat rate. Most units responded best to beat rates in the 4-8 Hz range. Sign-selectivity was observed only when the jamming signal (S2) was presented through electrodes other than those used to deliver the mimic (S1) of the fish's EOD, i.e. only when amplitude modulations were accompanied by modulations of differential phase. Intracellular studies suggest that most sign-selective neurons of the tectum are large, multipolar cells in the stratum album centrale. These cells send projections to the reticular formation, to lamina 9 of the torus semicircularis and to the N. electrosensorius.     

Copper ions and hydrogen peroxide form hypochlorite from NaCl thereby mimicking myeloperoxidase

Sea urchins have elaborated multiple defenses to assure monospermic fertilization. In this work, we have concentrated on a study of the mechanism(s) by which hydrogen peroxide (H₂O₂) prevents polyspermy in Arbacia punctulata. We found that it is not H₂O₂ but probably hypochlorous acid/hypochlorite (HOCl/OCl^?) derived from H₂O₂ that is toxic to the supernumerary sperm. The spermicidal activity of H₂O₂ is potentiated by at least one order of magnitude by cupric ions (Cu²⁺). This increased toxicity is not due to the formation of hydroxyl radicals (·OH) because ·OH scavengers did not counteract the activity of Cu²⁺. More-over, substitution of Cu²⁺ by ferrous ions (Fe²⁺), which are known to cause formation of ·OH from H₂O₂, had no effect on fertilization even at 10²?10³ times higher concentrations. In contrast, 3-amino-1,2,4-triazole (AT), an HOCl/OCl^? scavenger, totally reversed the toxic effects of Cu²⁺. Furthermore, we found that HOCl/OCl^? is generated in solutions of H₂O₂ and Cu²⁺ in the presence of 0.5 M NaCl and that its accumulation is abolished by AT. Thus it is possible that the antifertility properties of copper are due to its ability to mediate formation of HOCl/OCl^?. HOCl/OCl^? generated by Cu²⁺ from H₂O₂ and Cl^?, a low concentration of exogenously added HOCl/OCl^?, or increased concentrations of H₂O₂ has similar inhibitory effects on the fertilization process in sea urchins. Therefore, we suggest that polyspermy is prevented by the action of a myeloperoxidase that affects the formation of HOCl/OCl^? from the Cl^? present in sea water through reaction with H₂O₂ generated by the newly fertilized egg.     

Neem (Azadirachta indica) cultivated in Haiti

So that valuable products from the neem tree (Azadirachta indica) will be readily available in the future, countries in the neotropics should emulate Haiti and grow the species where it thrives even in eroded, semiarid, depauperate areas suitable for few other trees.