Physiological studies on pea tendrils. XIII. Respiration is necessary for contact coiling

When 9 day old light grown pea ( Pisum sativum L. cv. Alaska 2B) plants are irrigated for 4–6 days with 50 μ M 4-chloro-5-(dimethylamino)-2-(α, α, α-trifluoro- m -totyl)-3(2H)-pyridazinone, designated San-6706, the new leaves and tendrils grow morphologically normal, but with neither chlorophyll nor the ability to carry out photosynthesis. Excised tendrils from these plants coil in response to rubbing as well as those from water irrigated controls. Tendrils from San-6706 irrigated plants, which have been dark adapted for 2 or 3 days, proceed to coil when illuminated, just as do those from water irrigated plants. Rubbing of dark adapted tendrils results in an increased respiration rate over the first hour or two, when most of the coiling response occurs. Inhibitor studies indicate that blockage of oxidative phosphorylation, but not of the alternative, cyanide-insensitive, path of respiration, results in a failure of tendrils to coil in response to mechanical perturbation. It is concluded that the normal path of respiration, perhaps via ATP production, may be necessary for thigmosensory perception leading to contact coiling in pea tendrils.     

Platelet-activating factor in human luteal phase endometrium

Platelet-activating factor (PAF; 1-O-alkyl-2-acetyl-sn-glycero-3-phosphorylcholine) is one of the most potent mediators of vascular permeability. PAF levels change in the rabbit endometrium just prior to implantation, which suggests that PAF may be a key substance transducing preimplantation embryonic signals. To study whether PAF was present in the human endometrium, and if so, to determine the cellular origin and hormonal regulation of endometrial PAF, specimens were obtained from 14 women (aged 23-42 yr) undergoing elective hysterectomy during the luteal phase of the cycle (plasma progesterone levels greater than 2 ng/ml). No specimens were taken from women with malignant uterine pathology. Stromal cells and epithelial glandular cells were separated by collagenase and DNAse digestion, and then cultured to confluence in vitro in medium 199. Radioimmunoassays of prostaglandin F (PGF) and prolactin in the culture media were used to confirm cell type and viability. PGF release into the culture medium from stromal cells was low (control 1.52 +/- 0.20 ng/ml), and unchanged by hormone treatment. In contrast, release of PGF from unstimulated glandular cells was 6.05 +/- 0.52 ng/ml, and was significantly increased (p less than 0.05) by estradiol or progesterone plus estradiol, to 12.17 +/- 1.67, and 8.60 +/- 0.81, respectively. Progesterone alone was without effect. Prolactin was secreted by stromal cell cultures, increasing steadily from 24 to 120 h. The levels in the medium were increased by progesterone. PAF activity was assessed by rabbit platelet aggregation and serotonin-release bioassays after lipid extraction and separation by thin-layer chromatography.(ABSTRACT TRUNCATED AT 250 WORDS)     

Adenylat-Pools in Plastiden,Mitochondrien und einer Restzytoplasma-Fraktion,bestimmt unter in vivo-Bedingungen und in Abhängigkeit von Differenzierungsvorgängen

Es wird eine Methode beschrieben, die es ermöglicht, Mesophyllprotoplasten innerhalb von 60 sec in Fraktionen weitgehend unkontaminierter Plastiden, nur schwach durch andere Zellkompartimente verunreinigter Mitochondrien und ein Restzytoplasma zu zerlegen. In Verbindung mit einer weitgehenden Beendigung von Stoffwechselreaktionen ermöglicht diese Technik die Bestimmung von Metaboliten in verschiedenen Zellkompartimenten unter in vivo-Bedingungen. Dies wird gezeigt am Beispiel Plastiden, Mitochondrienund Zytoplasma-assoziierter Adenylatkonzentrationen im Verlauf der Etioplasten-Chloroplasten-Transformation. Die Ergebnisse deuten darauf hin, daß, obwohl kurz nach Beginn der Belichtung in der Zelle vorübergehend stark erhöhte Adenylatkonzentrationen auftreten, die Energieladung 2(ATP)+(ADP)/2([ATP]+[ADP] +[AMP]) der verschiedenen Kompartimente konstant bleibt. Wir danken Dr. S. P. Robinson, H. Wirtz und Prof. R. R. Theimer für wertvolle Anregungen und der Deutschen Forschungsgemeinschaft für finanzielle Unterstützung.     

Group chorusing as an intragroup signal in the greater ani,a communally breeding bird

Group living often requires maintaining dynamic and varied relationships with fellow group members, while simultaneously monitoring and interacting with external competitors. Group members in many social species vocalize together to produce duets or choruses—coordinated, often conspicuous vocal displays—that may play a role in these interactions. Compared with male–female duets, however, relatively little research exists on the function and adaptive significance of group choruses, which involve three or more individuals. Here we investigate chorusing behavior in the greater ani (Crotophaga major), a communally breeding cuckoo that nests in stable social groups of four to eight unrelated individuals. Groups may remain together for several years on the same nesting territory, and groups occasionally destroy each other's clutches in conflicts over high-quality territories. We asked whether the raucous, highly stereotyped choruses performed by ani groups are primarily used for intra- or intergroup communication, and whether they contain information about the identity of the social group and the number of birds vocalizing. Behavioral observations and acoustic recordings from three breeding seasons revealed that choruses typically occurred during social interactions within the group (78% of choruses) or in response to a predator or extra-group individual (17%) and only rarely in intergroup interactions (4%). Consistent with this finding, choruses did not reliably reflect the number of birds vocalizing, and we found only limited evidence for group-specific acoustic signatures (driven by a single group whose choruses were highly distinct). These results suggest that group choruses play an important role in intra-group signaling, potentially in contexts such as group formation, reinforcement of social bonds within the group, and/or collective decision-making, and they motivate new research questions about the role of collective signaling in social evolution.     

A simple rule reduces costs of extragroup parasitism in a communally breeding bird

How do cooperatively breeding groups resist invasion by parasitic "cheaters," which dump their eggs in the communal nest but provide no parental care [1,2]? Here I show that Greater Anis (Crotophaga major), Neotropical cuckoos that?nest in social groups containing several breeding females [3], use a simple rule based on the timing of laying to recognize and reject eggs laid by extragroup parasites. I experimentally confirmed that Greater Anis cannot recognize parasitic eggs based on the appearance of host egg phenotypes or on the number of eggs in the clutch. However, they can discriminate between freshly laid eggs and those that have already been incubated, and they accordingly eject asynchronous eggs. This mechanism is reliable in naturally parasitized nests, because group members typically lay their?eggs in tight synchrony, whereas the majority of parasitic eggs are laid several days later. Rejection of asynchronous eggs therefore provides a rare empirical example of a complex, group-level behavior that arises through relatively simple "rules of thumb" without requiring advanced cognitive mechanisms such as learning, counting, or individual recognition.     

Lanthanide spectroscopic studies of the dinuclear and Mg(II)-dependent PvuII restriction endonuclease

Type II restriction enzymes are homodimeric systems that bind four to eight base pair palindromic recognition sequences of DNA and catalyze metal ion-dependent phosphodiester cleavage. While Mg(II) is required for cleavage in these enzymes, in some systems Ca(II) promotes avid substrate binding and sequence discrimination. These properties make them useful model systems for understanding the roles of alkaline earth metal ions in nucleic acid processing. We have previously shown that two Ca(II) ions stimulate DNA binding by PvuII endonuclease and that the trivalent lanthanide ions Tb(III) and Eu(III) support subnanomolar DNA binding in this system. Here we capitalize on this behavior, employing a unique combination of luminescence spectroscopy and DNA binding assays to characterize Ln(III) binding behavior by this enzyme. Upon excitation of tyrosine residues, the emissions of both Tb(III) and Eu(III) are enhanced severalfold. This enhancement is reduced by the addition of a large excess of Ca(II), indicating that these ions bind in the active site. Poor enhancements and affinities in the presence of the active site variant E68A indicate that Glu68 is an important Ln(III) ligand, similar to that observed with Ca(II), Mg(II), and Mn(II). At low micromolar Eu(III) concentrations in the presence of enzyme (10-20 microM), Eu(III) excitation (7)F(0) --> (5)D(0) spectra yield one dominant peak at 579.2 nm. A second, smaller peak at 579.4 nm is apparent at high Eu(III) concentrations (150 microM). Titration data for both Tb(III) and Eu(III) fit well to a two-site model featuring a strong site (K(d) = 1-3 microM) and a much weaker site (K(d) approximately 100-200 microM). Experiments with the E68A variant indicate that the Glu68 side chain is not required for the binding of this second Ln(III) equivalent; however, the dramatic increase in DNA binding affinity around 100 microM Ln(III) for the wild-type enzyme and metal-enhanced substrate affinity for E68A are consistent with functional relevance for this weaker site. This discrimination of sites should make it possible to use lanthanide substitution and lanthanide spectroscopy to probe individual metal ion binding sites, thus adding an important tool to the study of restriction enzyme structure and function.     

A unique surface pattern and micropylar apparatus in the eggs of Luciocephalus sp. (Perciformes, Luciocephalidae)

A hitherto undescribed Luciocephalus species was bred in captivity for the first time. The male mouthbrooders spawned about 80 slightly pear-shaped eggs with a diameter varying from 2-2 to 3-4 mm. The enveloping zona radiata measured 15 μm in thickness. In the SEM the outer surface of the zona radiata showed a pattern which is unique among all teleosts studied to date. Many of the numerous, virtually parallel ridges extended from the vegetal to the animal pole. There they spiralled towards the micropyle and terminated in its pit. The role of such a surface pattern as a sperm guidance system was discussed.     

Scanning electron microscopic observations on the head morphology of seven different leptocephali belonging to six eel families (Anguilliformes)

Scanning electron microscopy observation was carried out on head morphology, number and construction of teeth, nostril position and the presence of neuromasts of seven species of leptocephali from six families of the Anguilliformes. The number and form of the teeth vary within the different families, from 76 teeth inGnathophis sp. (Congridae) to 32 teeth inAnarchias yoshiae (Muraenidae). In most of the genera the number of teeth on upper and lower jaws is almost equal, except inGnathophis sp.,Anguilla anguilla andKaupichthys hyoproroides. The unusual size and form of the leptocephali's teeth led us to speculate on the feeding behaviour of these larvae. Tentatively we suggest that the tooth formation of the leptocephali may act as a filtering system, rather than as a predatory apparatus, as its vicious appearance might suggest. Given the largely passive nature of a filtering system, the larvae would be able to concentrate on their migration. Of all the investigated leptocephali, onlyNemichthys scolopaceus shows one olfactory opening on each side of the head, whilst all the other species show two openings. The data obtained from these investigations suggest that teeth form as well as form and position of the nostrils are characteristics of the genera, and possibly also of the species.     

Elektronenmikroskopische Untersuchungen an den Oralcirren und der Haut vonBranchiostoma lanceolatum

Praeoral tentacles and epidermis of the anterior body region ofBranchiostoma lanceolatum Pallas have been investigated by electron microscopy. The epidermis of the praeoral tentacles and the anterior body region are mono-layered and cohere by strong denticulations of the adjoining cell walls. Vertical secretory vesicles at the cell surface give off mucous substances. The secretory vesicles are found only in the body epithelium. Between epithelium cells both epithelia contain two different secondary sensilla types.B. lanceolatum is the lowest chordate in which taste buds of the praeoral tentacles have been found. The taste buds overtop the surface of the epithelium. The praeoral tentacles are stiffened by a skeleton rod, situated asymmetrically and build up in layers. The skeleton rod is surrounded by connective tissue, which includes a coelomic space. Axon bundles of different strength are situated in the connective tissue. Not only the taste buds but also singular sensilla types are innervated by these axon bundles. The relatively strong basement lamina is partially zonated and contains pores. An antagonistically arranged layer of collagen fibres of varying thickness occurs below the basement lamina.