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  • 2015-2019
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  • 1986  (52,321)
  • 1
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    Springer
    Insectes sociaux 33 (1986), S. 118-131 
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Resume 1. La distribution des individus de groupes normaux deMyrmica rubra a été étudiée dans des nids artificiels formés d'une seule rangée de cellules. Une couche d'ouvrières recouvre les reines et le couvain, ménageant cependant une région périphérique où l'on ne trouve que des ouvrières dont le rôle est de défendre l'entrée et de préparer les proies pour la consommation. La région périphérique est particulièrement bien représentée, près de l'entrée. Lorsque le paquet d'œufs grossit, l'enveloppe d'ouvrières se dissocie et découvre les larves; lorsque ces dernières sont prêtes à se nymphoser, les ouvrières les ramènent vers le centre où se trouvent le couvain non alimenté et les reines. 2. La sociabilité des reines est très variable. Certaines restent seules la plupart du temps alors que d'autres sont rarement solitaires et se regroupent avec d'autres reines. Certaines des reines sociables peuvent être très attentives au choix de leurs compagnes alors que d'autres sont tout à fait indifférentes à leur voisinage. Toutes les reines pondent des œufs en nombre variable sans rapport avec leur degré de sociabilité.
    Notes: Summary 1. The form of normal groups ofMyrmica rubra has been studied in artificial nests consisting of a single tier of cells. An envelope of workers spreads out and covers the queens and brood leaving a cortex composed only of workers that functions as a defensive zone and a zone in which prey are prepared for ingestion. The cortex is especially well developed near the entrance. As the egg cluster grows, it breaks up, often with worker help and releases larvae; when these are ready to pupate the workers take them back into the central core of non-feeding brood and queens. 2. The sociability of queens varies from those that are often alone, to those that are rarely alone and spend most of their time with other queens. Sociable queens may be very specific in the individuals they associate with or very indifferent to their companions. All the queens lay eggs in variable numbers but the quantity is not related to their sociability.
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  • 2
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    Insectes sociaux 33 (1986), S. 45-58 
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Wir berichten hier die Ergebnisse unserer Studien anPrionopelta amabilis, die erste genauere Untersuchung dieser pantropischen Gattung mit den kleinsten Arbeiterinnen in dem sehr primitiven Tribus Amblyoponini. 1. P. amabilis Kolonien wurden in verfaulenden Holzstämmen und Baumästen am Boden des Regenwaldes von Costa Rica gefunden. Zwei Kolonien, die sehr sorgfältig aus dem Holz abgesammelt wurden, enthielten eine Königin und eine für den Tribus Amblyoponini ungewöhnlich grosse Population von Arbeiterinnen. Eine Kolonie, die auch jungfräuliche Weibchen enthielt, hatte über 700 Arbeiterinnen. 2. P. amabilis erbeutet bevorzugt Dipluren, sie nehmen aber auch einige andere Arthropoden als Beutetiere an. Die Beute wird direkt an die Larven verfüttert. Die Königin erhält trophische Eier, die offensichtlich von den Arbeiterinnen gelegt werden. 3. Eine schwache, doch deutlich erkennbare, Arbeitsteilung zwischen verschiedenen Altersklassen existiert. Damit unterscheidet sichP. amabilis vonAmblyopone pallipes, die enzige andere Amblyoponine, die in dieser Hinsicht untersucht wurde. Jüngere Arbeiterinnen pflegen Brut und Königin. Aeltere Arbeiterinnen sind vorwiegend Futtersammler. Wie zu erwarten sind die Ovarien der Arbeiterinnen, die die Königin pflegen besser entwickelt, als die der Furagierameisen. 4. Soziales Trageverhalten unter adulten Ameisen konnte nicht beobachtet werden. Während Nestemigrationen wird nur die Brut transportiert. Ein merkwürdiges Schleifen der Hintertarsen bei einzelnen Arbeiterinnen könnte dem Spurenlegen oder der Substratmarkierung dienen. 5. Die Nestkammern, in denen Puppen gehalten werden, sind häufig mit alten Puppenkokonteilchen tapeziert. Das dient offensichtlich dazu, die Puppenkammern trockener zu halten.
    Notes: Summary We report here the first detailed account of a member ofPrionopelta, a pantropical genus possessing the smallest workers in the primitive ant tribe Amblyoponini. 1. Colonies ofP. amabilis were found nesting in small rotting logs and tree branches on the floor of primary rain forest in Costa Rica. Two that were more carefully excavated possessed a single dealate queen and a worker population unusually large for Amblyoponini. One of the latter colonies, which was in the process of eclosing alate queens (during late March), contained over 700 workers. 2. P. amabilis workers prey preferentially on campodeid diplurans, although they also accept (less readily) a limited variety of other small arthropods. The prey are given directly to the larger larvae. The queen is fed trophic eggs which we infer to have been laid by the workers. 3. A moderately well-marked temporal division of labor occurs, thus distinguishingP. amabilis fromAmblyopone pallipes, the only other amblyoponine hitherto studied in this regard. Younger workers attend the brood and queen, forming a retinue around the latter individual. Older workers are more active in foraging. As expected, the ovaries are better developed in workers associated with the queen than in foragers. 4. Emigration to nest sites is conducted individually, with the workers carrying brood but not other adult nestmates. A foot-dragging behavior, possibly associated with trail-laying, is described. Alarm pheromones are apparently absent. 5. A unique “wall-papering” behavior was also discovered: the workers line the pupal chambers with fragments of discarded pupal cocoons, rendering these spaces drier and hence presumably more suitable for pupal occupation.
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  • 3
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    Insectes sociaux 33 (1986), S. 59-69 
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Erebomyrma, eine neotropische Gattung des Tribus Pheidologetini, hat nicht nur einen mitPheidole konvergenten Kastendimorphismus, sondern gleichtPheidole auch in der Form der Arbeitsteilung. Die Soldaten (major Kaste) vonE. nevermanni, helfen bei der Ueberwältigung von Beute, verteidigen das Nest, und dienen als Speichertier für flüssige Nahrung. Bei Anwesenheit der minor Arbeiterinnen haben sie ein begrenztes und spezialisiertes Verhaltensrepertoire, das jedoch erweitert wird (einschliesslich Nahrungssammeln und Brutpflege), wenn die minor Arbeiterinnen entfernt werden. Gleichlaufend mit dieser Bereicherung des Verhaltensrepertoires erfolgt eine etwa zehnfache Zunahme der allgemeinen Aktivität. Weitere Einzelheiten zur Biologie und zum Sozialverhalten vonE. nevermanni werden berichtet. Am bemerkenswertesten ist das »Verteidigungs-Gefolge« um die Königin, das verstärkt wird, wenn die Kolonie offen gelegt wird; die Nutzung von Sammelstrassen; das Erbeuten von Arthropoden-Eiern; und das Fehlen von sozialem Trageverhalten unter adulten Ameisen bei Kolonieemigration.
    Notes: Summary Erebomyrma, a Neotropical genus of pheidologetine ants with caste dimorphism convergent to that ofPheidole, also resemblesPheidole in its pattern of division of labor. The major workers ofE. nevermanni, the species examined during this study, assist in subduing larger prey, defend the nest, and serve as semi-repletes in liquid food storage. Their repertory is limited and specialized when minor workers are present but expands to include foraging and brood care when the minor workers are removed. The expansion is accompanied by a 10X or more increase in general activity rate. Other details of the natural history and social behavior ofE. nevermanni are given. The most distinctive properties include the occurence of defensive retinues around the queen which intensify when the colony is exposed, the use of trunk trails during foraging, predation on arthropod eggs, and the absence of adult transport during colony emigration.
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  • 4
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    Insectes sociaux 33 (1986), S. 85-99 
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Freiland- und Laboratoriumsuntersuchungen einer Kolonie vonMyrmoteras toro, die im Central Sulawesi gesammelt wurde, und einerM. barbouri Kolonie von Singapore, lieferten die ersten ökologischen und verhaltensbiologischen Informationen über diese wenig bekannte Gattung der Unterfamilie Formicinae. Die Arbeiter jagen einzeln und fangen mit ihren langen Schnapp-Kiefern kleine weiche Evertebraten, ähnlich wie es von Arten der Dacetini und Odontomachini bekannt ist. Bevor die Jägerinnen zuschnappen öffnen sie Kiefer um 280°. Das ist der grösste Mandibel-Offnungswinkel, der bisher von Ameisen bekannt ist. Bei der Nestverteidigung werden Eindringlinge häufig mit den Mandibeln gestossen. M. toro jagt kleine, weiche Arthropoden, währendM. barbouri nahezu ausschliesslich Springschänze fängt. Ich nehme an, dass die Trigger-Haare, die typisch fürM. barbouri und andere Arten der UntergattungMyrmoteras sind, eine spezielle Anpassung für das Collembolenjagen sind. Rekrutierung zu Futter und Nestplätzen scheint nicht vorzukommen.
    Notes: Summary Field and laboratory studies on a colony ofMyrmoteras toro collected in Central Sulawesi and aM. barbouri colony from Singapore have provided the first ecological and behavioral information on this enigmatic formicine genus. Both species capture prey singly by the trap-jaw method, much as do many dacetine and odontomachine ants. Before striking the ants open their jaws 280°, the greatest degree yet recorded in the ants. Also, the nest area is defended from encroachment by other invertebrates by slapping intruders repeatedly with the mandibles. M. toro workers catch a variety of small, soft-bodied arthropods.M. barbouri preys largely or entirely on springtails. I hypothesize that the trigger hairs characteristic ofM. barbouri and other species of the subgenusMyrmoteras could represent an adaptation to collembolan prey. Recruitment to food (sugar baits) and during emigrations appears to be absent.
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  • 5
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    Insectes sociaux 33 (1986), S. 101-102 
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
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  • 6
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Summary The role of antennal contacts made by the donor worker on the receiver's head during trophallactic interactions among Ants (Camponotus vagus) was investigated by studying the food flow characteristics: amount of foodstuff transmitted, duration and speed of transmission. For this purpose, we either removed both the donors' antennal funicles or tied their scape/funicule articulations in the flexed position. The parameters of food transmission between control workers were found to depend on seasonal factors: the consequences of both antennal removal and immobilization were therefore analysed for each season separately. The workers with antennal lesions gave more food than control workers in spring and summer. On the contrary, in autumn the lesions did not bring about any significant change. The antennal contacts made by the donor on the receiver's head might be involved in the regulation of trophallactic food transmission, at least in spring and summer.
    Notes: Resume Nous avons recherché quel est, lors des interactions trophallactiques entre ouvrières de Fourmi (Camponotus vagus), le rôle des contacts antennaires effectués par l'ouvrière donneuse sur la tête de la receveuse, quant aux caractéristiques du flux: quantité de nourriture transmise, durée, vitesse de transmission. Dans ce but, nous avons pratiqué soit l'ablation des funicules antennaires de la donneuse, soit l'immobilisation, en position pliée, des articulations scape/funicule. Chez les témoins, les caractéristiques du flux trophallactique varient avec la saison. Il en est de même pour les effets de l'ablation ou de l'immobilisation, qui ont donc été étudiés séparément pour chaque saison. Au printemps et en été, les ouvrières opérées donnent plus de nourriture que les ouvrières intactes. En automne, au contraire, l'opération n'entraîne pas de modification significative. Il apparaît que, du moins au printemps et en été, les contacts des antennes de l'ouvrière donneuse peuvent intervenir dans la régulation du flux trophallactique.
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  • 7
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    Insectes sociaux 33 (1986), S. 105-117 
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Die zwei untersuchtenPseudomyrmex-Arten haben die folgenden Kommunikationssysteme: a) P. triplarinus informiert ihre Nestgenossinnen über das Vorhandensein von Futter, aber nicht über dessen Lage.P. termitarius hat keinerlei Kommunikation bei der Futtersuche. b) Beide Arten erkennen ihr Territorium anhand von Duftstoffen.P. triplarinus markiert ihr Territorium mit einem Pheromon aus dem Thorax, wahrscheinlich von der Metathorakaldrüse. Die territoriale Markierung hat eine Lebensdauer von einer halben bis einer Stunde. Sie dient wahrscheinlich der Verteidigung des Territoriums. Die Markierung vonP. termitarius hält über 5 Stunden an und wirkt wahrscheinlich als Nesteingangs-Orientierungsmarke. Die Herkunft des Duftstoffes ist nicht klar. c) P. triplarinus benützt ein Pheromon aus dem Kopf als Signal für das Erkennen ihrer Schwestern.P. termitarius verwendet nicht-identifizierte Duftstoffe, die überall im Körper vorhanden sind, als Identifikationssignal. d) Beide Arten haben Alarmpheromone im Kopf und im Abdomen. Die Kommunikationssysteme werden im Zusammenhang mit der oekologischen Adaption der Arten analysiert.
    Notes: Summary The twoPseudomyrmex species studied have the following communication systems: a) P. triplarinus informs its nestmates about the presence of food, but not about its location.P. termitarius does neither. b) Both species recognize their territory and/or area around the nest entrance through odours on the substrate.P. triplarinus marks its territory with a pheromone from the thorax, probably from the metapleural gland. This territorial mark lasts less than 1 h, and probably advertises at least part of the home range of the colony. The territorial odour used byP. termitarius, probably works as a nest entrance orientation mark, and lasts over 5 h, but less than 24 h. The origin of the odour is not clear. c) P. triplarinus uses a cephalic pheromone as the main signal for nestmate recognition.P. termitarius uses non-identified odours, present on all body parts of the insect, as a nestmate recognition signal. d) Both species produce alarm pheromones from the head and the gaster. The communication systems are interpreted in relation to the ecological adaptations of each species.
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  • 8
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Resume Les ouvrières deLeptothorax unifasciatus différencient de nouvelles aires de celles précédemment explorées. En effet, un comportement de «va-et-vient» apparaît plus fréquent sur un papier vierge que sur un papier familier à la colonie. La chute d'activité sur un papier vierge après quelques heures indique que ce dernier devient rapidement familier à la colonie dans le dispositif expérimental utilisé. Les expériences suggèrent que le territoire est modifié chimiquement par l'activité des fourmis, mais la possibilité d'un marquage chimique n'a toutefois pas été explorée. Trois facteurs contrôlent le niveau d'activité de fourragement chezL. unifasciatus: 1o la nature de l'aire de récolte (connue ou inconnue); 2o la taille de la société; 3o le temps de séjour de la société dans un même nid. Des sociétés établies récemment dans leur nid montrent un niveau d'activité de fourragement plus élevé sur une aire de récolte inconnue que sur une aire familière. Dans tous les cas, il existe une relation linéaire liant la taille de la société et son activité. Des sociétés établies depuis longtemps dans un même nid montrent toujours une activité inférieure aux sociétés récemment établies. Aucune différence n'est observée entre une aire de récolte inconnue et familière. De plus, la taille de la société apparaît être moins influente sur son activité générale que pour une société récemment établie dans son nid. Ces résultats sont interprétés en termes éco-éthologiques, tenant compte d'une caractéristique biologique essentielle des sociétés deL. unifasciatus: les déménagements fréquents, saisonniers ou liés à la précarité des nids.
    Notes: Summary Leptothorax unifasciatus workers differentiate new areas from those previously explored. Indeed, a “coming and going” behaviour appears more frequent on a virgin paper than on a familiar one. The decrease of activity on a new paper after some hours indicates that this species rapidly gets to known such an area in the experimental device used here. The experiments suggest that the area is chemically modified by the ants' activity, but the possibility of a specific marking behaviour was not further investigated. Three factors control the level of foraging activity inL. unifasciatus: 1o. The nature of the foraging area (familiar or virgin). 2o. The size of the society. 3o. The age of the nest-site. Societies newly established in their nest show a higher level of foraging activity on a virgin area than on a familiar one. In every case, there is a linear relation between the size of the society and its activity. Long-settled societies always show a lower activity than recently established ones, and no difference was observed when they recruited on a virgin and a familiar area. Moreover, the society size appears to be less important in determining the general level of activity than for recently-settled societies. These results are tentatively interpreted in eco-ethological terms, taking into account a main biological characteristic ofLeptothorax societies: frequent nest emigrations that are either seasonal or due to fragile nest-sites.
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  • 9
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Resume Dans un article précédent nous avons étudié au laboratoire la production des diverses catégories de descendants durant la vie de la colonie. Nous étudions ici plus particulièrement la durée de vie propre de ces diverses catégories. La durée de vie des femelles montre une distribution bimodale et nous avons discerné des guêpes «à vie courte» et «à vie longue». Un chevauchement existe entre les phases de production de ces deux catégories. Il existe une relation entre la date de l'orphelinage, la proportion des femelles «à vie courte» et le sex ratio de la descendance. Les colonies précocement orphelines ont, en fait, une descendance totale accrue, mais cette descendance est surtout mâle et parmi les femelles produites, les guêpes «à vie courte» sont les plus nombreuses.
    Notes: Summary In a previous paper we described a study under laboratory conditions of the pattern of development of the various categories of descendants during the life of a colony; the present study is particularly concerned with the duration of life-span of these various categories. The life-spans of females showed a bimodal distribution and short-lived and long-lived wasps were distinguished. Considerable overlap was observed between the periods during which these two categories of wasp emerged. A relationship was found to exist between the date of orphanship, the percentage of “short-lived” females and the sex ratio of the offspring. Colonies which lost their queen as early as June showed an increase in the number of descendants produced, but these descendants were predominantly male and, among the females, the majority were “short-lived”.
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  • 10
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    Insectes sociaux 33 (1986), S. 388-405 
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Summary The analysis of the possibilities of localization of prey by foraging workers shows that the maximal distance is 3 mm.eThe whole behaviour sequence includes the following phases: detection, localization, approach, antennation, attack with abrupt mandible closure, lifting, stinging and transport. A sequential analysis establishes that antennation is more emphasized when the prey is immobilized or is anaesthetized with CO2. In this last case, the prey is seized by a slow closure of the mandibles of the ant which is followed by transport to the nest. The lifting and stinging phases are more frequent when the living prey is larger. In this case, the attack is insufficient to kill or to knock out the prey which struggles to pull away. After a failure during an attempt of capture the ant presents a new behaviour allowing a quick localization of the prey.
    Notes: Resume L'analyse des possibilités de localisation des proies par les ouvrières pourvoyeuses montre que la distance maximale est de 3 mm. La séquence comportementale la plus riche, lors de la capture de la proie, comprend les phases suivantes: détection, localisation, approche, palpation antennaire, attaque avec fermeture brusque des mandibules, soulèvement, piqûre et transport. Une analyse séquentielle montre que la palpation est la plus intense quand la proie s'immobilise ou est anesthésiée au CO2. Dans ce dernier cas, la proie est saisie à la suite d'une fermeture lente des mandibules suivie aussitôt du transport vers le nid. Les phases de soulèvement et de piqûre sont d'autant plus fréquentes que la proie vivante est plus grosse. En effet, dans ce cas, l'impact de l'attaque est insuffisant pour tuer ou étourdir la proie qui se débat afin de se dégager. A la suite d'un échec au cours d'une tentative de capture, un comportement particulier permet aux fourmis de retrouver leur proie.
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  • 11
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Resume Neuf colonies du termite inférieurIncisitermes schwarzi, résidant dans les longs et étroits troncs morts de manglier, ont été sectionnées sur le terrain; les découpes ont été reportées au laboratoire et dans chaque section les termites ont été classés selon leur sexe et leur caste. Dans une série distincte d'observations, des portions des colonies ont été introduites dans un étroit tunnel et ultérieurement la position, le sexe et la caste de chaque individu furent enregistrés. Les données résultant de ces deux études indiquent que les sexes sont répartis au hasard parmi la colonie de termites; aussi bien à l'intérieur des castes qu'entre différentes castes. La seule exception était la légère tendance des soldats d'un sexe donné à s'associer avec les individus du sexe opposé d'une autre caste. Les observations ne soutiennent pas la thèse selon laquelle la parenté génétique des individus du même sexe et de même parents (dû à la multiplicité des chromosomes sexuels) et la préférence sexuelle du comportement altruiste, in fluencent l'évolution de l'eusocialité des termites.
    Notes: Summary Nine colonies of the lower termiteIncisitermes schwarzi, inhabiting tall, narrow dead mangrove tree trunks, were sectioned in the field; the sections were taken back to the laboratory and the termites in each section were classified by sex and caste. In a separate series of observations, portions of colonies were introduced into a narrow tunnel, and later the position, sex, and caste of each individual were recorded. The data from both kinds of study indicate that the sexes are distributed randomly within the termite colony, both within castes and between castes. The only exception was a slight tendency for soldiers of one sex to be associated with non-soldiers of the opposite sex. The observations do not support the idea that the close genetic relatedness of same-sex siblings (due to multiple sex chromosomes) and preferential sex-biased altruistic behavior underly the evolution of eusociality in termites.
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  • 12
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    Pure and applied geophysics 124 (1986), S. 31-52 
    ISSN: 1420-9136
    Keywords: Fault gouge ; friction ; deformation textures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The frictional properties of a crushed granite gouge and of gouges rich in montmorillonite, illite, and serpentine minerals have been investigated at temperatures as high as 600°C, confining pressures as high as 2.5 kbar, a pore pressure of 30 bar, and sliding velocities of 4.8 and 4.8×10−2 μm/sec. The gouges showed nearly identical strength behaviors at the two sliding velocities; all four gouges, however, showed a greater tendency to stick-slip movement and somewhat higher stress drops in the experiments at 4.8×10−2 μm/sec. Varying the sliding velocity also had an effect on the mineral assemblages and deformation textures developed in the heated gouges. The principal mineralogical difference was that at 400°C and 1 kbar confining pressure a serpentine breakdown reaction occurred in the experiments at 4.8×10−2 μm/sec but not in those at 4.8 μm/sec. The textures developed in the gouge layers were in part functions of the gouge type and the temperature, but changes in the sliding velocity affected, among other features, the degree of mineral deformation and the orientation of some fractures.
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  • 13
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    Pure and applied geophysics 124 (1986), S. 79-106 
    ISSN: 1420-9136
    Keywords: Deformation ; faults ; cataclasis ; gouge ; rock mechanics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Field observations of the Punchbowl fault zone, an inactive trace of the San Andreas, are integrated with results from experimental deformation of naturally deformed Punchbowl fault rocks for a qualitative description of the mechanical properties of the fault and additional information for conceptual models of crustal faulting. The Punchbowl fault zone consists of a single, continuous gouge layer bounded by zones of extensively damaged host rock. Fault displacements were not only localized to the gouge layer, but also to discrete shear surfaces within the gouge. Deformation in the exposure studied probably occurred at depths of 2 to 4 km and was dominated by cataclastic mechanisms. Textural data also suggest that significant amounts of pore fluids were present during faulting, and that fluid-assisted mechanisms, such as dissolution, diffusion, and precipitation, were operative. The experimental data on specimens collected from the fault zone suggest that there is a gradual decrease in strength and elastic modulus and an increase in relative ductility and permeability toward the main gouge zone. The gouge layer has fairly uniform mechanical properites, and it has significantly lower strength, elastic modulus, and permeability than both the damaged and the undeformed host rock. For the Punchbowl fault and possibly other brittle faults, the variations in loading of the gouge zone with time are primarily governed by the morphology of the fault and the mechanical properties of the damaged host rock. In addition, the damaged zone acts as the permeable unit of the fault zone and surrounding rock. It appears that the gouge primarily governs whether displacements are localized, and it therefore may have a significant influence on the mode of slip.
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  • 14
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    Pure and applied geophysics 124 (1986), S. 141-157 
    ISSN: 1420-9136
    Keywords: Seismic refraction ; mylonites ; fractures ; seismic reflection ; low velocity zone ; microcracks
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The internal properties within and adjacent to fault zones are reviewed, principally on the basis of laboratory, borehole, and seismic refraction and reflection data. The deformation of rocks by faulting ranges from intragrain microcracking to severe alteration. Saturated microcracked and mildly fractured rocks do not exhibit a significant reduction in velocity, but, from borehole measurements, densely fractured rocks do show significantly reduced velocities, the amount of reduction generally proportional to the fracture density. Highly fractured rock and thick fault gouge along the creeping portion of the San Andreas fault are evidenced by a pronounced seismic low-velocity zone (LVZ), which is either very thin or absent along locked portions of the fault. Thus there is a correlation between fault slip behavior and seismic velocity structure within the fault zone; high pore pressure within the pronounced LVZ may be conductive to fault creep. Deep seismic reflection data indicate that crustal faults sometimes extend through the entire crust. Models of these data and geologic evidence are consistent with a composition of deep faults consisting of highly foliated, seismically anisotropic mylonites.
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    Pure and applied geophysics 124 (1986), S. 269-288 
    ISSN: 1420-9136
    Keywords: Cataclasites ; ductile shear zones ; microstructures
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    Topics: Geosciences , Physics
    Notes: Abstract Brittle-to-ductile shear zones from two separate geological settings are shown to have nucleated on zones of predominantly brittle deformation. The shear zones are not simply foliated cataclasites, since they contain abundant evidence of dynamic recrystallization of constituent minerals. A small quartz diorite lens in the Borrego Springs shear zone, southern California, contains centimeter-scale cataclasite zones that exhibit a gradual transition into foliated rock. Alteration of magnesiohornblende to actinolite, feldspar to white mica plus quartz, and biotite to chlorite, produced elongate minerals that define the foliation. During the later stages of deformation, intracrystalline slip and dynamic recrystallization of quartz and feldspar were important deformation mechanisms. The widespread occurrence of mineralized dilatant cracks predated the development of meter-to-decimeter-scale ductile shear zones in the Striped Rock granite, southern Virginia. Again, important deformation mechanisms in the final stages of deformation were intracrystalline slip and dynamic recrystallization of quartz. In both field areas the role of fluids has been important from the onset of brittle deformation. Fluids may have enhanced early fracturing in addition to causing the alteration and hydrolytic weakening of host rock minerals and the introduction of new mineral species. Each of these processes is thought to have contributed to the later localization of crystal plastic deformation in the rocks.
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  • 16
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    Pure and applied geophysics 124 (1986), S. 383-414 
    ISSN: 1420-9136
    Keywords: Rock friction ; constitutive behaviour ; granite ; stability of sliding ; earthquake
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    Topics: Geosciences , Physics
    Notes: Abstract An understanding of the frictional sliding on faults that can lead to earthquakes requires a knowledge of both constitutive behavior of the sliding surfaces and its mechanical interaction with the loading system. We have determined the constitutive parameters for frictional sliding of initially bare surfaces of Westerly granite, using a recently developed high pressure rotary shear apparatus that allows long distances of sliding and therefore a greater assurance of attaining steady state behavior. From experiments conducted at room temperature and normal stresses of 27–84 MPa several important results have been found. (1) A gouge layer 100 to 200 μm thick was developed from the initially bare rock surfaces after 18 to 70 mm of sliding. (2) The steady state frictional resistance, attained after about 10 mm of sliding, is proportional to the negative of the logarithm of the sliding velocity. (3) Abrup changes in the velocity of sliding result in initial changes in the frictional resistance, which have the same sign as the velocity change, and are followed by a gradual decay to a new steady state value over a characteristic distance of sliding. This velocity weakening behavior is essentially identical with that found by several previous workers on the same material at lower normal stress. (4) Our results are well described by a two state variable constitutive law. The values of the constitutive parameters are quite similar to those found previously at low normal stress, but the characteristic distance is about an order of magnitude smaller than that found at 10 MPa normal stress with thicker layers of coarser gouge. (5) We have approximated our results with a one state variable constitutive law and compared the results with the predictions of existing nonlinear stability analysis; in addition, we have extended the stability analysis to systems possessing two state variables. With such formulations good agreement is found between the experimentally observed and theoretically predicted transitions between stable and unstable sliding. These results allow a better understanding of the instabilities that lead to earthquakes.
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  • 17
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    Pure and applied geophysics 124 (1986), S. 515-529 
    ISSN: 1420-9136
    Keywords: Slip rate ; stress drop ; fault ; heterogeneity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Recent observations made by Kanamori and Allen about earthquake recurrence time and average stress drop revealed a very interesting relation: earthquakes with longer recurrence times have higher average stress drops. They attributed the difference in stress drop to the difference in long-term average slip rate. To interpret their result in terms of the healing effect, we simulated earthquake recurrence with a one-dimensional mass-spring model, incorporating a recently developed rate-and-state dependent friction law for different loading rates and heterogeneous strength distributions. We first calculated the stress drop and recurrence time as functions of loading rate for a homogenous fault model. We found that the stress drop increases up to 30% when the loading rate decreases from 10 cm/yr to 0.01 mm/yr. Thus, the observed great variability of stress drop, from a few bars to a few hundred bars, which is obtained by replotting the data of Kanamori and Allen in the form of stress drop versus long-term slip rate, may not be attributable to the healing effect alone. Our numerical simulation shows that the variability may be due primarily to the spatial heterogeneity of strength on the fault. Our simulation also suggests that of the two empirical laws that were inferred from the same laboratory friction data, called the power law and the logarithmic law by Shimamoto and Logan, the former can explain the observed relation between stress drop and slip rate better than can the latter, at least for strike-slip fault. The logarithmic law is an earlier and simpler version of the rate-state-dependent friction law.
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  • 18
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    Pure and applied geophysics 124 (1986), S. 793-810 
    ISSN: 1420-9136
    Keywords: Plate models ; shear and tensile source mechanisms ; seismotectonic interpretation
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    Topics: Geosciences , Physics
    Notes: Abstract A special experimental technique enabled us to study in detail seismic events on a fault model in a uniaxial stress field. The recording system used made it possible to investigate the radiation pattern for all the events observed including the precise determination of the dislocation origin. The aim of the present paper is (1) to find the relation between shear and tensile displacements, (2) to check a possible influence of the process of tensile crack generation on the seismic energy release and (3) to compare the seismic regime of a single fault before and after the tensile crack generation, respectively. Results prove the dominating importance of shear mechanism for the seismic energy release. The tensile displacement can be seismoactive only under special contact conditions on the fault plane. The existence of tensile cracks at the fault tips changed the pattern of seismic energy radiation. This feature is probably caused by subsequent changes in contact conditions on the fault plane and in the stress field around the fault. A comparison of some results of the present model experiments with the already published results of geological and seismological measurements and investigations shows the analogous character in laboratory and in nature of the process of tectonic earthquake preparation, the displacement course on the fault during the earthquake and the manner of seismic energy release on faults.
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  • 19
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    Pure and applied geophysics 124 (1986), S. 811-824 
    ISSN: 1420-9136
    Keywords: Earthquake modelling ; fracturing process ; precursors of failure
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    Topics: Geosciences , Physics
    Notes: Abstract One of the simplest models of earthquakes and rockbursts was studied in laboratory conditions in which the fracture was initiated in a barrier between two preexisting faults. The treated models were built of concrete; during the construction of the models, the stress concentrators were inserted inside the models. This arrangement enabled the shear displacement to occur during uniaxial loading of the model. The tests were made on the series of models, the sizes of which were mutually varying more than one order. In the process of the barrier fracture propagation, the following were investigated: the time and space changes of local deformations as well as the acoustic emission, velocities and amplitudes of elastic waves, electrical conductivity and proper electro-induction. The process of barrier fracturing can be understood in three fundamental stages. In the course of the first stage, the density of small tensile cracks increases considerably, while the volume in which they exist is gradually enlarged. In the second stage, as the result, of these cracks coupling, longer shear cracks are created. During the coupling, due to the development of numerous regions of unstable deformation, the zones of nonequal rigidity arise in the treated medium, distributed within it in a mosaic-like pattern. In the third stage, the main fracture is prepared and formed with simultaneous unloading of the surrounding medium. The process of crack forming is gradually localized into a more narrow zone. The second and third stages of fracture forming are reflected in variations of all the above-mentioned physical parameters which are therefore identified as the precursors of the main fracture. By means of the series of precursors it is possible to find the reliable prediction of a barrier fracture.
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    Pure and applied geophysics 124 (1986), S. 857-874 
    ISSN: 1420-9136
    Keywords: Fault interaction ; seismotectonic interpretation
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    Topics: Geosciences , Physics
    Notes: Abstract Systems of two parallel linear faults of the same length with the angle of inclination α=45° were investigated under uniaxial linearly increasing load. Perspex plates were used as models. For each treated fault configuration the morphology of tensile cracks and the sequence of seismoacoustic events of shear and tensile origin were studied. It is shown that the seismic regime of a fault system is strongly influenced by the contact conditions on a fault plane; it is different in the faults with the aseismic contact, represented by open slits, and in the faults with the seismoactive contact, represented by filled slits, respectively. The experiments proved the dominating role of a fast shear displacement of the stick-slip type in the regime of seismic energy release of a fault system. The tensile crack generation seems to be only of little—if not negligible—importance. On the other hand, the existence of tensile cracks in a fault system can play an important role in the course of subsequent loading cycles because the stick-slip displacements can take place not only along the primary faults but also along the planes of tensile cracks. A comparison of some results of model experiments and the already published results of geological and seismological investigations indicated that the way of seismic energy relase on faults in nature and in the laboratory could be of the same character. Several analogies between the seismic regime of a fault model and of real seismic regions were found concerning the morphology of faults, off-fault fore- and aftershocks, and earthquake doublets, respectively.
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  • 21
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    Pure and applied geophysics 124 (1986), S. 487-513 
    ISSN: 1420-9136
    Keywords: Friction law ; magnitude-frequency relation ; seismicity simulation
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    Topics: Geosciences , Physics
    Notes: Abstract The dynamic motions and stabilities of a single-degree-of-freedom elastic system controlled by different friction laws are compared. The system consists of a sliding block connected to an elastic spring, driven at a constant velocity. The friction laws are a laboratory-inferred friction law called the rate-and-state-dependent friction law, proposed by Dieterich and Ruina, and a simple friction law described by dynamic and static frictions. We further extend the solution to a one-dimensional mass-spring model which is an analog of a fault controlled by the rate-and-state-dependent friction law. This model predicts non uniform slip and stress drop along the rupture length of a heterogeneous fault. This result is very different from some earlier modelings based on the simple friction law and a slip weakening friction law. In those earlier modelings the stress and slip functions become smoother with time along the length of the fault rupture, owing to the interactions between fault segments during slip. Because of this smoothing process the number of small events will decrease with time, and the universilly observed stationary magnitude-frequency relation cannot be explained. The interaction between a fault segment and its neighboring segments can be measured when the post-slip stress on this segment is compared with the stress on an identical segment (represented by a block in this modeling) without neighboring segments. If the post-slip stress of the former is much higher than that of the latter, strong interaction exists; if the two are close, only weak interaction exists. The interaction is determined by the relative motion between fault segments and the time duration of interaction. Our new modeling with the rate-and-state-dependent friction law appears to show no such smoothing effect and provides a physical mechanism for the roughening process in the difference between the fault strength and stress that is necessary to explain the observed stationary magnitude-frequency relation. The noninstantaneous healing predicted by the rate-and-state-dependent friction law may be repsonsible for the recurring nonuniform slip and stress drop, and may be explained by the reduction of interaction among fault segments due to the low frictional strength during the fault stopping. The very low friction during slip stopping allows much longer times than does the higher friction due to instantaneous healing for the fault segments to adjust their motions from an upper-limit slip velocity to almost rest. According to newton's second law, a process with fixed masses and constant velocity changes involves low forces and weak interactions if it is accomplished in a long time period, and vice versa. Our modeling also indicates that the existence of strong patches with higher effective stress on a fault is needed for the occurrence of major events. The creeping section of a fault, such as the one along the San Andreas fault in central California, on the other hand, can be simulated with the rate-and-state-dependent friction law by certain model parameters, which, however, must not include strong patches. In this case small earthquakes and aseismic creep relieve the accumulating strain without any large events.
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  • 22
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    Pure and applied geophysics 124 (1986), S. 531-566 
    ISSN: 1420-9136
    Keywords: Fault mechanics ; earthquakes ; crustal deformation ; San Andreas fault
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    Topics: Geosciences , Physics
    Notes: Abstract A two-dimensional model for stress accumulation and earthquake instability associated with strike-slip faults is considered. The model consists of an elastic lithosphere overlying a viscous asthenosphere, and a fault of finite width with an upper brittle zone having an elastoplastic response and a lower ductile zone having an elastoviscoplastic response. For the brittle, or seismic, zone the behavior of the fault material is assumed to be governed by a relation which involves strain hardening followed by a softening regime, with strength increasing with depth. For the fault material in the ductile, or aseismic, section, the viscous effect is included through use of a nonlinear creep law, and the strength is assumed to decrease with depth. Hence, because of the lesser strength and the viscous effect, continuous flow occurs at great depths, causing stress accumulation at the upper portion of the fault and leading to failure at the bottom of the brittle zone. The failure is initially due to localized strain softening but, with further flow, the material above the softened zone reaches its maximum strength and begins to soften. This process accelerates and may result in an unstable upward rupture propagation. Relations are developed for the history of deformation within the lithosphere, specifically for the velocity of particles within the fault and at the ground surface. The boundary-element method is used for a quantitative study, and numerical results are obtained and compared with the recorded surface deformation of the San Andreas fault. The effects of geometry and material properties on instability, on the history of the surface deformation, and on the earthquake recurrence time are studied. The results are presented in terms of variations of ground-surface shear strain and shear strain rate, and velocity of points within the fault at various times during the earthquake cycle. It is found that the location of rupture initiation, the possibility of a sudden rupture as opposed to stable creep, and also the ground deformation pattern and its history, all critically depend on the mechanical response of the material within the fault zone, especially that of the brittle section. Shorter earthquake recurrence times are obtained for shallower brittle zones and for a stiffer lithosphere. Lower viscosities of the aseismic zone and the absence of asthenospheric coupling tend to suppress instability and promote stable creep. The model results thus suggest that the overall viscosity of the ductile creeping zone must exceed a minimum value for a sudden upward propagating rupture to take place within the seismic section.
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    Pure and applied geophysics 124 (1986), S. 609-610 
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    Development genes and evolution 195 (1986), S. 1-9 
    ISSN: 1432-041X
    Keywords: Rana esculenta complex ; Protein synthesis ; Embryogenesis ; Heat shock ; Amphibian oocyte
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    Topics: Biology
    Notes: Summary We have used isotopic labelling and both one-and two-dimensional electrophoretic procedures to analyse the protien synthesis patterns in oocytes and early embryos of three phenotypes of the European green frogs. The results demonstrated that protein patterns of Rana ridibunda and R. esculenta are identical, but that they differ from those of R. lessonae. Progeny of the lethal cross R. esculenta × R. esculenta showed a distinct delay in the appearance of stage-specific proteins during early embryogenesis. The heat-shock response of R. ridibunda and R. esculenta oocytes was found to be identical, but different from that of Xenopus laevis. The implications of these findings, with respect to hybridogenesis in R. esculenta complex and variations in the regulations of heat shock genes in different amphibian species, are discussed.
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    Development genes and evolution 195 (1986), S. 10-14 
    ISSN: 1432-041X
    Keywords: True hermaphroditism ; Domestic fowl ; Testis graft
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    Topics: Biology
    Notes: Summary Two types of hermaphroditism were experimentally induced in genetically female fowls by grafting of embryonic testes in embryos. Of the 27 hermaphrodites observed during the 8 months after hatching, 20 possessed a right testis and a left ovary and 7 a right testis and a left ovotestis. The testes and ovotestes contained seminiferous tubules with a more or less developed germ cell complement, attaining in many cases the early spermatid stage. The interstitial tissue was poorly functional, as shown by the absence of male secondary sex characters. The ovary or ovarian part of the ovotestes possessed numerous small ovarian follicles. The female arrangement of the plumage and the absence of spurs demonstrated the secretion of oestrogens. A mechanism is proposed for explaining this partial masculinization of genetically female gonads, a phenomenon which occurs during the period of embryonic sex differentiation, and is responsible for this experimental true hermaphroditism.
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    Development genes and evolution 195 (1986), S. 33-38 
    ISSN: 1432-041X
    Keywords: Hydractinia ; Hydra ; Homarine ; Nicotinamide ; Pattern formation
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    Topics: Biology
    Notes: Summary Homogenate of coelenterate tissue interferes with metamorphosis in Hydractinia and pattern formation in both Hydractinia, and Hydra. From the extracts two fractions comprising low-molecular-weight compounds with strong metamorphosis-inhibiting activity were separated. One of these contains, as the active compound, homarine (N-methyl picolinic acid). Homarine concentrations down to 10−6 mol/l stop or retard metamorphosis. High concentrations block the continuation of metamorphosis as long as they are maintained in the culture medium and treatment with homarine during metamorphosis influences the proportioning of the future polyp's body pattern. Most of the homarine found in Hydra tissue derives from Artemia given as food. It is not identical with inhibitor I, an activity partially purified from Hydra tissue, which prevents head and foot formation in Hydra.
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  • 27
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    Keywords: Drosophila embryogenesis ; Segmentation ; Genetic mosaics
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    Topics: Biology
    Notes: Summary In order to investigate the localized requirements for the activity of genes that are required in a Drosophila embryo for segmentation, we have analyzed the patterns in genetic mosaics. In this paper, we describe our results with four different X-chromosome linked segmentation loci: armadillo, fused, giant and unpaired. For each locus, we first describe in detail the cuticle phenotype of mutant embryos. We then describe the segmentation patterns in embryos mosaic for these mutations, in each case utilizing the shavenbaby (svb) larval cuticle marker mutation to identify the regions of pattern made by genetically mutant cells. For all four loci, we can identify embryos containing large regions of both mutant and wildtype pattern. In these mosaics the regions of mutant pattern are marked with svb and the genetically wildtype (svb +) cells make wildtype pattern. The interpretations of the patterns in embryos mosaic for fused and unpaired are complicated by the variability of the phenotypes. However, after taking these complications into account, our principal conclusion is that the requirement for embryonic gene activity seems to be primarily cell autonomous. Based on the descriptions of the mutant phenotypes of these four loci and the analysis of the mosaics, we speculate on the possible roles these genes play in the process of segmentation.
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    Development genes and evolution 195 (1986), S. 39-48 
    ISSN: 1432-041X
    Keywords: Brachydanio ; Cortical granule exocytosis ; Ionophore A23187 ; Localized ionophoretic stimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effects of the divalent ionophore A23187 upon unfertilized eggs of the freshwater teleost fish, Brachydanio rerio, have been examined by light, scanning (SEM) and transmission (TEM) electron microscopy. Treatment of eggs with micromolar amounts (1 μM, 10 μM) of A23187 triggers cortical granule exocytosis and elevation of the chorion. However, the exocytosis of cortical granules in ionophore-activated eggs is explosive and occurs more rapidly than in eggs naturally activated in conditioned tap water. Eggs treated with A23187 in a medium lacking extra-cellular calcium also show cortical granule exocytosis, suggesting strongly that egg activation in Brachydanio results from release of calcium primarily from intracellular stores; however, there is a distinct delay in the onset of cortical granule breakdown. Unfertilized eggs exposed to A23187 for 1–5 min show noticeable disturbances in cell surface topography, including loss of microplicae and the appearance of prominent membrane-limited blebs. To determine if cortical granule exocytosis is self-propagating once initiated, A23187 was applied to a localized portion of the unfertilized egg surface, using either a G-50 sephadex gel bead or a 1 mm glass capillary tube. Eggs placed in continuous contact for 15 min with a bead coated with 10 μM A23187 show neither exocytosis of cortical granules nor elevation of the chorion. All eggs exhibit exocytosis when positioned against a glass rod coated with 1 μM A23187. The cortical granule breakdown is partial and restricted to less than 50% of the egg surface in most cells. The complete exocytosis of cortical granules in the zebra danio egg appears to require the stimulation and release of calcium from multiple sites over the cortex.
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  • 29
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    Development genes and evolution 195 (1986), S. 409-416 
    ISSN: 1432-041X
    Keywords: Immunohistochemistry ; Tissue distribution of LDH5 ; Developing chicken embryos
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    Topics: Biology
    Notes: Summary The distribution of A(M) subunits of lactate dehydrogenase (mainly LDH5) in developing muscle, heart, liver, lung, kidney and cartilage tissue of chicken embryos was examined by the indirect fluorescent antibody technique. Antibodies against porcine LDH5, purified by affinity chromatography, were used for this purpose. In special areas of newly formed myofibrils in somitic myoblasts fluorescence was already detected after 4 days of incubation, and located at the same place in muscle tissue of all advanced developmental stages examined. During the myotube stage of muscle development staining was also located in the peripheral thickened cytoplasma of the myotubes. The myocardium did not exhibit any fluorescent staining in the developmental stages examined. Endocardium, epicardium and pericardium, however, were fluorescent in young developmental stages. The liver showed fluorescence in 5- to 8-day embryos mainly in the endothelial cells of the blood sinusoids. In 9- to 12-day embryos the bile ducts became fluorescent. In lungs after 9- to 12-day development the epithelium and the surrounding tissues of bronchi exhibited strong immunofluorescence. The mesonephros exhibited faint granular fluorescence in tubule-forming cells and their membranes after 4–9 days of incubation. Advanced developmental stages only exhibited fluorescent blood cells. This latter staining is at least partly due to non-specific reactions of blood cell membranes with FITC-conjugated anti-rabbit IgG. Cartilage is characterized by non-specific fluorescence, but in embryos older than 8 days strong granular fluorescence of chondrocytes and staining of the perichondrium distinguished sections treated with anti-LDH5 antibodies from control sections reacted only with FITC-conjugated anti-rabbit IgG. In addition, strong fluorescent staining was detectable in certain areas of the 5-day neural tube and faint staining in the mucosa of the intestine from embryos older than 10 days.
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  • 30
    ISSN: 1432-041X
    Keywords: Embryogenesis ; Maternal effect mutant ; Morphogenetic determinant ; Pattern formation ; UV irradiation
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    Topics: Biology
    Notes: Summary The embryonic body pattern of Chironomus samoensis, as well as other chironomids, can be altered dramatically by irradiating their eggs with ultraviolet light (UV). Anterior UV irradiation leads to the formation of double abdomen embryos whose anterior segments are replaced by posterior segments with reversed polarity. Most double abdomens are symmetrical showing a mirror image duplication of the posterior six or seven segments. However, in some cases the anterior end of the double abdomen is shorter, and comprises fewer segments, than its posterior counterpart. These asymmetries range from moderate to extreme. They involve the juxtaposition, at the plane of polarity reversal, of disparate segments. The same range of symmetrical and asymmetrical double abdomens is also formed spontaneously in an apparently mutant strain of C. samoensis. There are striking similarities between this natural variant and the Drosophila melanogaster mutant bicaudal which are also discussed with respect to models of embryonic pattern formation.
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  • 31
    ISSN: 1432-041X
    Keywords: Determination ; Polar lobe ; Unequal cleavage ; Spiralians
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    Topics: Biology
    Notes: Summary The inequality of the first cleavage division of the Chætopterus embryo is caused by the production of a small polar lobe and the internal shifting of the first cleavage spindle. This division produces a two-celled embryo containing a small AB and a large CD blastomere. These blastomeres have different morphogenetic potentials. Only the larvae resulting from isolated CD blastomeres are able to form bioluminescent photocytes, eyes and lateral hooked bristles. The removal of the polar lobe during first cleavage does not have a great effect on development. These lobeless embryos display a normal pattern of cleavages through the time of mesentoblast formation. The resulting larvae are essentially normal, however they do not form functional photocytes. If the CD cell is isolated after the removal of the first polar lobe, the resulting larva is virtually identical to those formed by the intact CD cell except it lacks the photocyte cells. These results indicate that two separate pathways are involved in the segregation of developmental or morphogenetic potential which takes place during first cleavage. One set of factors, which are necessary for photocyte formation, are associated with the first polar lobe. Other factors that are necessary for the formation of the eyes and lateral hooked bristles are segregated by the unequal cleavage which results from an internal shifting of the cleavage spindle. The removal of a large portion of the vegetal region of the embryo during first cleavage leads to the production of larvae which display a decreased ability to form eyes and lateral hooked bristles. These embryos frequently display an abnormal pattern of cleavages. They do not form the primary somatoblast or the mesentoblast. These results indicate that the vegetal region of the CD cell of Chætopterus is analogous to polar lobes which have been studied in other species, and is therefore important in the specification of the D quadrant. These features of the first cleavage of Chætopterus are a combination of those displayed by forms with direct unequal cleavage and other forms which cleave unequally through the production of large polar lobes. The significance of these findings is discussed relative to the origins of these different types of unequal cleavage.
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  • 32
    ISSN: 1432-041X
    Keywords: Histones ; Sea urchins ; Regulation of gene expression ; Maternal messenger RNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ability to specifically delete the store of maternal α-subtype histone mRNAs stored in the egg pronucleus has allowed us to examine the role of this major fraction of the maternal mRNA in the early development of the sea urchinStrongylocentrotus purpuratus. The egg nucleus was removed by centrifugation, and the resulting enucleate half eggs were fertilized. These haploid andromerogones lacked any stored α-subtype histone mRNAs. However, when grown in parallel with control embryos, they showed identical cleavage cycles, cell numbers, and patterns of cell differentiation. Measurements of the amount of α-histone mRNA in these andromerogones showed that there was no premature synthesis of α-histone mRNAs to compensate for the deleted maternal pool. Instead embryonic synthesis was normal in timing of initiation and duration. the ability of these embryos to develop into highly differentiated larvae without their maternal α-subtype histone mRNA pool suggests that this pool is not a critical component of early development per se. This suggestion is strengthened by the observation that the primitive sea urchinEucidaris tribuloides naturally lacks this maternal histone mRNA store. Evolutionary implications are discussed.
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    Development genes and evolution 195 (1986), S. 259-264 
    ISSN: 1432-041X
    Keywords: Pattern formation ; Cell differentiation ; Gene organization ; Gene regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We studied the genetic bases of threeHairy-wing (Hw 1,Hw Ua ,Hw 49c ) mutations mapping in the region of theachaete-scute complex (AS-C). Analysis of X-ray-induced revertants ofHw 1 andHw 49c uncoveredachaete andscute mutant phenotypes respectively. This indicates that theHw mutant phenotypes result from an excess of function of these genes of theachaete-scute complex (AS-C). The phenotypes of the differentHws show allelic specificity in the pattern of extrachaetes. In addition to these mutations, certain inversions and internal duplications of the AS-C also produce aHw-variegated phenotype, probably due to variegation or decompensation of the genes of the AS-C. The expressivity of the differentHws (mutation or variegation) is modulated by the number of doses of the AS-C present in the genome. A similar dose-dependent modulation is exerted by the transregulatory geneshairy andextramacrochaetae. We discuss these results on the basis of a regulation model of the expression of the AS-C.
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    ISSN: 1432-041X
    Keywords: Extracellular matrix ; Mollusca ; Mesoderm determination ; Lectins ; Cell contacts
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    Notes: Summary In 32-cell stage embryos ofPatella vulgata one of the macromeres contacts the animal micromeres, and as a result is induced to differentiate into the stem cell of the mesodermal cell line. In this study we show the presence of an extracellular matrix (ECM) between these two interacting cell types. The ECM appears to be formed by the micromeres during the 32-cell stage. Staining experiments with alcian blue and tannic acid indicate that in contains glycoconjugates, possibly in the form of proteoglycans. The characteristics of the ECM were examined further by fluorescein isothiocyanate (FITC)-lectin labelling. Of 17 lectins tested, concanavalin A (ConA), succinyl-ConA, LCH-B (Lens culinaris) and PEA (Pisum sativum) showed a positive labelling of the ECM. These results are in accordance with the electron microscopic data. The appearance of the ECM at this specific stage and place suggests that it might play an important role in the induction of the mesodermal cell line.
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  • 35
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    Development genes and evolution 195 (1986), S. 281-289 
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    Keywords: Sensory neurons ; Peripheral nervous system ; Pathway formation ; Drosophila embryo ; Neurogenesis
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    Notes: Summary The thoracic and abdominal segments of the Drosophila embryo contain 373 neurons innervating external sensory structures and 162 neurons innervating chordotonal organs. These neurons are arranged in ventral, lateral and dorsal clusters within each segment, in a highly invariant pattern. Two fascicles are formed in each segment as the sensory axons grow ventrally towards the CNS and meet motor axons growing dorsally from the CNS. In all but the last segment, the anterior fascicle is contributed by the dorsal and lateral neurons, while the posterior one is formed by the ventral neurons. Five distinct segmental patterns are described, corresponding to (1) the prothorax, (2) the other two thoracic segments, (3) the first seven abdominal segments, (4) the eighth and (5) the ninth (and possibly the tenth) abdominal segments.
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    Development genes and evolution 195 (1986), S. 338-343 
    ISSN: 1432-041X
    Keywords: Drosophila melanogaster ; Imaginai discs ; Aldehyde oxidse ; Determination ; Field size
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    Topics: Biology
    Notes: Summary The pattern of aldehyde oxidase (AO) activity was determined in wing discs of Drosophila melanogaster larvae homozygous for the mutants apt 73n, Beaded, and vestigial (vg) in order to determine if reduction in field size in the pouch could be related to alterations of the wild-type AO pattern, as suggested by the Kauffman (1978) hypothesis. The pattern in wild-type discs was resolved into six areas for comparison with mutant discs. vg discs developed at 25° C showed restriction of the pattern into a small area on the anterior side of the disc, and comparison of vg and wild-type prepupal wings allowed positive identification of the AO pattern elements which remained. AO patterns in vg wing discs grown at 27°, 29°, and 31° C were progressively more complete and similar to wild-type, reflecting the reduction in cell death in discs grown at higher temperatures. These results show that cell loss during the third instar in vg development at 25° C is responsible for the alteration of the AO pattern, rather than field size reduction, and that determination of the pattern must take place much earlier than the time of its first appearance during the third larval instar, and before cell death in vg discs begins. Thus mutants acting at earlier stages will be necessary for further tests of the Kauffman hypothesis.
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  • 37
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    Development genes and evolution 195 (1986), S. 417-432 
    ISSN: 1432-041X
    Keywords: Gene regulation ; Developmental pathways ; Antennapedia and Bithorax complexes in Drosophila
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    Notes: Summary We have studied the embryonic and adult phenotypes of genetic combinations between Polycomb (Pc), Regulator of bithorax (Rg-bx) and the genes of the Bithorax complex (BX-C) and the Antennapedia complex (ANT-C). The products of Pc and Rg-bx genes act antagonistically, their mutant combinations leading to the ectopic expression of genes of the BX-C and ANT-C. The genetic analysis of the Pc locus suggests it is a complex gene. Pc+ products behave as members of a “regulatory set” that negatively control the expression of BX-C and ANT-C genes. Genetic combinations between different doses of Pc, Rg-bx and the genes of the BX-C and ANT-C have phenotypes which may be interpreted as resulting from ectopic derepression of posterior selector genes repressing selector genes of anterior segments. The transformation phenotypes of certain genetic combinations differ in embryos and adults. A model of regulation of the BX-C and the ANT-C genes during the imaginal cell proliferation is presented, in which the specification state is maintained by self-activation of a given selector gene and down modulation of other selector genes in the same cell.
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    Development genes and evolution 195 (1986), S. 15-21 
    ISSN: 1432-041X
    Keywords: δ-crystallin ; Chick embryonic brain ; Cell culture ; Ectopic expression
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    Topics: Biology
    Notes: Summary Expression of δ-crystallin, a lens-specific protein, in 6-day-old chick embryonic brain cells was examined in situ and in vitro. The presence of minute amounts of δ-crystallin and its mRNA (δ-mRNA) in brain cells in situ was demonstrated by immunoblot and Northern blot analysis. In spreading cultures of the brain cells, δ-crystallin and δ-mRNA showed a significant increase from their in situ level. Immunohistological staining (peroxidase antiperoxidase) with monospecific anti-serum against δ-crystallin revealed that δ-producers were both epithelial cells and dendritic cells. Neither lentoidogenesis nor α-crystallin expression was observed. Stimulation of δ-crystallin synthesis in cultured brain cells differed when compared with transdifferentiating cultures of neural retina cells. In the latter, δ-crystallin synthesis occurred concomitantly with differentiation of morphologically distinct lens cells containing α-crystallin.
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  • 39
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    Development genes and evolution 195 (1986), S. 22-32 
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    Keywords: Drosophila ; Cell lineage ; Malpighian tubules ; Compartments ; Cell death
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    Notes: Summary Genetically marked maroon-like (mal) clones were induced by mitotic recombination with X-rays at the blastoderm stage in mal/mal + heterozygotes and were analysed in differentiated Malpighian tubules (MT). Marked cells were not confined to single anterior (MA) or posterior (MP) tubules, but were distributed among the four tubules. About 70% of the clones with two or more cells were fragmented, i.e. mal cells were separated by wild-type cells. Since the clones contain, on average, 6 cells and the differentiated MT consist of 484 cells (2 × 136 MA cells, 2 × 106 MP cells), we estimate that there are about 80 cells in the blastoderm anlage which on average pass through two to three mitoses. With increasing radiation doses (254 R, 635 R, 1270 R) a linear increase in clone frequency is observed. The mean sizes and size distributions of clones, however, remain unchanged. Since the increasing radiation dose also results in fewer differentiated Malpighi cells, we assume that regeneration does not occur. Therefore, size distributions of marked clones presumably represent real mitotic patterns in normogenesis. We suggest that essentially three successive mitoses take place, with a decreasing fraction of cells showing mitotic activity. Only a small fraction of cells goes through a fourth or even a fifth mitosis. Marked non-Minute clones induced in Minute heterozygotes are more frequent, but are not larger than non-Minute clones in wild-type background. Therefore, compartment boundaries cannot be recognized by this method. However, frequencies of marked cells found simultaneously in MA and MP pairs or in several single tubules of the same individuals are significantly higher than frequencies of multiple recombination events predicted by the Poisson distribution. From this, we conclude that neither the MA pair nor the MP pair nor single tubules represent compartments of the MT anlage.
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    Development genes and evolution 195 (1986), S. 117-122 
    ISSN: 1432-041X
    Keywords: Plasma membranes ; Amphibian embryogenesis ; Neural induction ; Xenopus laevis
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    Notes: Summary Plasma membranes were isolated in high yield from Xenopus gastrulae by repeated sedimentation in discontinuous sucrose gradients. Most of the yolk was separated by lowspeed sedimentation before centrifugation on the discontinuous sucrose gradients. The isolation of plasma membranes was followed by covalent labelling of the surface of dissociated gastrula cells with diazoniobenzene sulphonate, by electron microscopy and the distribution of enzymatic markers. The isolated plasma membranes have a low neural inducing activity as compared to other cell constituents.
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    Development genes and evolution 195 (1986), S. 123-127 
    ISSN: 1432-041X
    Keywords: Embryonic induction ; Nuclear fractions ; RNP particles ; Xenopus laevis
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    Notes: Summary From embryos (Xenopus laevis) of different developmental stages nuclei were isolated which exert neural inducing activity in the biological test. The active material could partly be extracted from the nuclei. Experiments for the isolation of nuclear ribonucleoprotein (RNP) particles have shown that the activity is localized at least in part in these particles. On the other hand, some neural inducer is not detached from chromatin and the nuclear matrix even with ionic detergents. Inducing activity was found in germinal vesicles and to a higher degree in the cytoplasm of oocytes, but in a masked, biologically inactive state.
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    Development genes and evolution 195 (1986), S. 128-132 
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    Keywords: Retinoids ; Pattern formation ; Cnidaria
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    Notes: Summary Retinoids have been shown to influence pattern formation in hydroid polyps (Hydractinia echinata) at various levels. These effects are counteracted by an inhibitor isolated from Hydra. The present study provides a theoretical attempt to elucidate the role of retinoids by computer simulations based on a simple model of pattern formation in Hydractinia. The elements of this model are morphogens of the Gierer-Meinhardt type, namely a long-range inhibitor and a short-range activator. From the calcualtions, a reducing effect of retinoids on the propagation of the inhibitor seems most probable.
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  • 43
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    Keywords: Amphibia ; Cleavage cycle ; Cleavage wave ; Asymmetry ; Time-lapse cinematography
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    Notes: Summary The animal and the dorsal side of five embryos of Xenopus laevis were studied in detail from the 7th to the 13th cleavage by means of time-lapse cinematography. At each cleavage the regionally ordered sequence of blastomere divisions is visible in the films as a “cleavage wave”, propagating about three times slower in the dorsal than in the animal view. In the dorsal view the waves run in an animal-vegetal direction, initially with a left-to-right deviation and in later cleavages converging on the region of the future blastopore. The lengthening of cleavage cycles begins at cycle 8 on the dorsal side, just above the future blastopore. From cycle 9 to 11 nearly equal lengthening occurs in each cycle at all animal-vegetal levels. In general, cycles lengthen a little more in median than in lateral sectors and a little more in right than in left sectors. Cycle 12 is longest in the sector above the future blastopore and shortest in the animal region. The results show that the initial pattern of a regionally ordered sequence of cleavage cycles of equal duration changes into a pattern of cycles of different durations as a result of gradual cycle lengthening, starting in the region just above the future blastopore and spreading in animal direction. The results are compared with data on the cleavage cycles of isolated blastomeres, and the possible relation with the induction of the mesoendoderm occurring during the stages studied is discussed.
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    Development genes and evolution 195 (1986), S. 489-498 
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    Keywords: Pole cells and midgut progenitors ; Cell lineages ; Embryogenesis ; Drosophila
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    Notes: Summary In this paper experiments concerning some aspects of the development of pole cells and midgut progenitors in Drosophila are reported. Cells were labelled by injecting horseradish-peroxidase (HRP) in embryos before pole bud formation and transplanted at different stages into unlabelled embryos, where the transplanted cells developed together with the unlabelled cells of the host. The hosts were then fixed and stained at different ages in order to demonstrate the presence of HRP in the progenies of transplanted cells. The main conlusions of the study are as follows. The gonads are the only organ to the formation of which pole cells normally contribute; those pole cells which do not participate in the formation of the gonads are finally eliminated or degenerate. Since the number of primordial germ cells in the gonads is the same irrespective of the number of pole cells present in the embryo, an (unknown) mechanism must exist regulating the final number of pole cells in each of the gonads. After their formation and before reaching the gonads, pole cells have been found to divide only up to two times. With respect to the midgut progenitors, the cells of both anlagen have been found to be committed to develop into midgut, although they behave as equivalent in that they do not apparently distinguish between the anterior and posterior anlage. Midgut progenitors have been found to divide a maximum of three times and to produce two different types of cells, epithelial cells of the midgut wall and spindle-like cells located internally in the gut.
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    Development genes and evolution 195 (1986), S. 506-512 
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    Keywords: Segment ; Pattern formation ; Insect egg ; Fragmentation ; Locust development
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    Notes: Summary The effect of transverse fragmentation on the segment pattern of the short germ embryo of the locust Schistocerca gregaria has been investigated at two stages subsequent to the formation of the germ anlage. Following fragmentation both anterior and posterior partial embryos were observed, although rarely in a single egg. Anterior partial patterns usually terminated with a segment visible at the time of fragmentation or with the next segment due to appear. Posterior partial patterns began with a wide range of segments depending on the level of fragmentation. Anterior and posterior partial patterns developing in a single egg were usually not complementary and the segments missing sometimes included some segments visible when the embryo was fragmented. Non-complementary patterns resulted following fragmentation in all regions, while complementary patterns only occurred after fragmentation in the visibly-segmented region. The results suggest that following fragmentation isolated posterior portions of the embryo continue to form segments, while isolated anterior regions usually do not. This effect could result from variable damage to an existing pattern of unequally-sized segment primordia, or from the disruption of a process of sequential segmentation in the elongating posterior region of the embryo. The results are broadly compatible with the progress zone model proposed by Summerbell et al. (1973).
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    Development genes and evolution 195 (1986), S. 533-533 
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    Development genes and evolution 195 (1986), S. 519-526 
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    Keywords: Mouse blastocyst ; Trophectoderm ; Inner cell mass ; Cleavage ; Cell death
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    Notes: Summary The numbers of cells in the trophectoderm (TE) and inner cell mass (ICM) of mouse blastocysts were counted by differentially labelling their nuclei with two polynucleotide-specific fluorochromes. Blastocysts recovered from the uterus at intervals between their formation early on Day 4 to the initial stages of implantation on day 5 were analysed. TE cell number increase was initially rapid, indicating some synchronisation of the sixth division, but slowed down progressively and plateaued on Day 5, possibly due to the onset of primary giant cell formation. ICM cell number increase was slower than the corresponding TE cells. As a result, TE cell number more than quadrupled, whereas ICM cell number only doubled over this period. Although the mitotic index of both populations of cells fell steadily, there was no significant difference between them. The decline in the proportion of ICM cells, therefore, is likely to be due to cell death, first detected in early blastocysts and predominantly located in the ICM. In addition, however, a contribution of ICM cells to the overlying polar TE cannot be excluded.
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    Development genes and evolution 195 (1986), S. 513-518 
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    Keywords: Regeneration ; Distal transformation ; Cell ; aggregation ; Cnidaria ; Hydractinia
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    Notes: Summary Polyps of mature colonies of Hydractinia echinata obey the “rule of distal transformation” by regenerating heads but not stolons. However, this rule is not valid for young polyps as these regenerate stolons from proximal cut ends. Also, small cell aggregates and even small fragments excised from full-grown polyps are capable of stolon formation. Aggregates produced from dissociated cells undergo either distal or proximal transformation depending on their size, speed of head regeneration in the donor used for dissociation and the positional derivation of the cells. The latent capability of stolon formation is released under conditions that cause loss of morphogens and depletion of their sources. However, internal regulative processes can also lead to gradual proximal transformation: regenerating segments of polyps sometimes form heads at both ends and the distal pattern is duplicated. Subsequently, all sets of proximal structures, including stolons, are intercalated. In contrast to distal transformation, proximal transformation is a process the velocity of which declines with the age and size of the cell community.
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  • 49
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    Development genes and evolution 195 (1986), S. 527-531 
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    Keywords: Drosophila oogenesis ; Pole cell transplantation ; Follicle polarity ; Germ line chimera
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    Notes: Summary In aberrant egg follicles of the pattern mutant dicephalic (dic) the oocyte is wedged in between two groups of nurse cells, and this condition may give rise to embryos which express anterior traits at both ends. We have analysed the role of the dic genotype of the germ line cells and the surrounding somatic follicle cells in the formation of the dic follicular phenotype. By means of pole cell transplantations into Fs (1) K 1237 hosts (this cell-autonomous mutation causes degeneration of the host's germ line cells early in oogenesis), we constructed chimeras in which either the follicle cells, the germ line cells, or both were homozygous for the dic mutation. In all three combinations the dic phenotype was expressed but not in controls with dic + in both germ line cells and follicular epithelium. Since follicles with the dic phenotype may be produced if either the germ line cells or the follicle cells lack dic + gene activity we suggest that cellular interactions between both cell types are required for the correct positioning of the oocyte at the follicle's posterior pole.
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    Development genes and evolution 195 (1986), S. 276-280 
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    Keywords: cAMP-analogues ; Sporangia morphogenesis ; HPLC ; Microinjection ; Physarum
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    Notes: Summary Plasmodial cells of the slime moldPhysarum polycephalum become competent for sporulation following a prolonged period of starvation in darkness. Then sporulation can be induced by illumination. Microinjections of the stable (Sp)- and (Rp)-diastereoisomers of adenosine cyclic 3′,5′ monothionophosphate before and during a sensitive period from the start of illumination until 5 h after lead to a significant delay in the sporulation process. Both of the diastereoisomers of cyclic AMP prolong the time for sporangia to form in darkness. However, the (Sp)-diastereoisomer is more effective and causes morphological changes in plasmodia. The experimental data suggest that cyclic AMP is decisively involved in light-induced differentiation in the lower eukaryotoPhysarum polycephalum.
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    Development genes and evolution 195 (1986), S. 290-295 
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    Keywords: Calliphora ; Fat body ; Calliphorin biosynthesis ; Larval serum proteins ; Gene polymorphism ; Transcription-translation uncoupling
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    Notes: Summary The stage- and tissue-specific biosynthesis of calliphorin was analysed during the development of the blowfly, Calliphora vicina. Western blot analyses show that the protein is not present in eggs, whereas it can be detected in fat body, brain, imaginai disk, salivary gland and epidermis throughout all postembryonic stages, including the adult one. By Northern analysis a unique 2.6 kb mol.wt. mRNA coding for calliphorin is identified exclusively in the fat body tissue of larvae, pupae and adults. Hybridization experiments of in vivo labelled poly(A)+ RNA with filter-bound calliphorin genes indicate that the genes are transcribed until pupariation. However, the translation of the calliphorin mRNA stops at the end of the feeding stage, as shown by [35S]-methionine incorporation.
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    Development genes and evolution 195 (1986), S. 296-301 
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    Keywords: Calliphorin ; Larval serum proteins (arylphorin) ; Cuticle ; Sclerotization ; Calliphora vicina
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    Notes: Summary The stage-specific appearance of calliphorin in cuticles of Calliphora vicina was analysed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting. The fate of the protein, injected into last instar larvae, was pursued by autoradiography of histological sections. Fractionation of sclerotized pupal cuticle in buffer-soluble, urea-soluble and NaOH-soluble fractions shows that calliphorin forms covalent and non-covalent links with other cuticle components. Calliphorin traverses the epidermal cells and enters the cuticle in an undegraded state and appears to be an important constituent of the sclerotizing system.
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    Development genes and evolution 195 (1986), S. 318-322 
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    Keywords: Drosophila melanogaster ; Operculum ; Bithorax complex ; Determination
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    Notes: Summary We have studied the course of the operculum line in the larval hypoderm of several bithorax complex mutants of Drosophila melanogaster. The bifurcation of the line, a characteristic of the first abdominal segment in wild-type (A1), can also appear in the metathoracic (T3) and other abdominal segments (A2, A3) depending on mutations within the bithorax complex. Therefore, we concluded that the course of the operculum line and thus the shape of the operculum is not determined by a suprasegmental gradient of positional information but by the functional state of the genes of the bithorax complex in each metamere. The dorsal and ventral branches of the operculum line react differently, the dorsal branch being more sensitive to the effect of loss of function mutations (bxd, iab-2 k), the ventral branch more affected by gain of function mutations (Hab). In some cases the effects of the mutations on the operculum line differed from those in the adult, suggesting a difference in sensitivity of larval hypodermal cells and histoblast cells to the functional gene products of the bithorax complex.
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    Development genes and evolution 195 (1986), S. 302-317 
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    Keywords: Drosophila ; Maternal effect Mutations ; Pattern formation
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    Notes: Summary Mutations in seven different maternal-effect loci on the second chromosome of Drosophila melanogaster all cause alterations in the anterior-posterior pattern of the embryo. Mutations in torso (tor) and trunk (trk) delete the anterior- and posterior-most structures of the embryo. At the same time they shift cellular fates which are normally found in the subterminal regions of the embryo towards the poles. Mutations in vasa (vas), valois (vls), staufen (stau) and tudor (tud) cause two embryonic defects. For one they result in absence of polar plasm, polar granules and pole cells in all eggs produced by mutant females. Secondly, embryos developing inside such eggs show deletions of abdominal segments. In addition, embryos derived from staufen mothers lack anterior head structures, embryos derived from valois mothers frequently fail to cellularize properly. Mutations in exuperantia (exu) cause deletions of anterior head structures, similar to torso, trunk and staufen. However in exu, these head structures are replaced by an inverted posterior end which comprises posterior midgut, proctodeal region, and often malpighian tubules. The effects of all mutations can be traced back to the beginning stages of gastrulation, indicating that the alterations in cellular fates have probably taken place by that time. Analysis of embryos derived from double mutant mothers suggests that these three phenotypic groups of mutants interfere with three different, independent pathways. All three pathways seem to act additively on the system which specifies anterior-posterior cellular fates within the egg.
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  • 55
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    Keywords: Segmentation ; DNA synthesis inhibitors ; Number of segments ; Character of segments ; Arthropoda
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    Notes: Summary The inhibitors of DNA synthesis change the differentiation of abdominal segments of the horseshoe crab and increase the number of segments in 90%–100% of the surviving embryos. The data suggest the following: 1. The primordia of segments are formed one by one from the cells at the posterior end of the embryonic area, and they are determined soon after formation. 2. When DNA synthesis inhibitors are applied, the forming primordium acquires a character intermediate between the anterior segment already determined and the segment next to be determined. 3. The abnormal differentiation is possibly caused by a time lag between DNA synthesis and the rest of metabolism. 4. The specific character of each segment of normal embryos and malformations successively determines that of the next segment. 5. By this route the whole number of segments is established.
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    Development genes and evolution 195 (1986), S. 334-337 
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    Keywords: Suppression ; P elements ; Lethality ; Drosophila
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    Notes: Summary In this paper we describe a new allele of suppressor of forked, su(f) hd37, referred to as hd37, which was isolated in a hybrid dysgenesis mutation screen and is shown to be P induced by its high frequency of reversion in hybrid dysgenic crosses, and by in situ hybridization. hd37 suppresses forked and fails to complement the forked suppression of known su(f) alleles. However, it complements the recessive lethality of alleles in both of the su(f) lethal complementation groups. We also describe a new phenotypic effect of su(f) alleles, the enhancement of Minute(3)i 55. Recessive lethal alleles enhance the lethal effects of this Minute, but hd37 does not. The temperature sensitive period for forked bristle suppression by hd37 was found to be very narrow, consisting of a short interval (12–18 h) immediately before bristle formation. These results suggest that the several genetic functions associated with this locus may be genetically separable.
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    Development genes and evolution 195 (1986), S. 355-358 
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    Keywords: Anuran amphibia ; Primordial germ cells ; Cellular migration ; Neural crest cells ; Endodermic morphogenesis
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    Notes: Summary The anlagen of neural tube or neural tube and neural crests were removed from toad embryos at the early neurula stage. The removal of the neural tube anlage does not affects the normal development of embryos. The removal of neural tube plus neural crest anlagen results in major disturbances of both endodermal morphogenesis and primordial germ cell migration. The possible indirect influence of neural crest cells upon the migration of the primordial germ cells is discussed. The neural crests cells could be involved in the formation and/or release of an attractive morphogen from embryonic chordomesoderm responsible for the migration of the primordial germ cells.
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    Development genes and evolution 195 (1986), S. 359-377 
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    Keywords: Drosophila ; Blastoderm fate map ; Head segmentation ; Larval cuticle
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    Notes: Summary Embryos of Drosophila melanogaster were irradiated in the presumptive head region with a UV-laser microbeam of 20 μm diameter at two developmental stages, the cellular blastoderm and the extended germ band. The ensuing defects were scored in the cuticle pattern of the head of the first-instar larva, which is described in detail in this paper. The defects caused by irradiating germ band embryos when morphologically recognisable lobes appear in the head region were used to establish the segmental origin of various head structures. This information enabled us to translate the spatial distribution of blastoderm defects into a fate map of segment anlagen. The gnathal segments derive from a region of the blastoderm between 60% and 70% egg length (EL) dorsally and 60% and 80% ventrally. The area anterior to the mandibular anlage and posterior to the stomodaeum is occupied by the small anlagen of the intercalary and antennal segments ventrally and dorsally, respectively. The labrum, which originates from a paired anlage dorsally at 90% EL, is separated from the remaining head segments by an area for which we did not observe cuticle defects following blastoderm irradiation, presumably because those cells give rise to the brain. The dorsal and lateral parts of the cephalo-pharyngeal skeleton appear to be the only cuticle derivatives of the non-segmental acron. These structures derive from a dorso-lateral area just behind the putative brain anlage and may overlap the latter. In addition to the segment anlagen, the regions of the presumptive dorsal pouch, anterior lobe and post-oral epithelium, whose morphogenetic movements during head involution result in the characteristic acephalic appearance of the larva, have been projected onto the blastoderm fate map. The results suggest that initially the head of the Drosophila embryo does not differ substantially from the generalised insect head as judged by comparison of fate map and segmental organisation.
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    Development genes and evolution 195 (1986), S. 378-388 
    ISSN: 1432-041X
    Keywords: Drosophila nasutoides ; Nuclear differentiation ; Timing ; Tissue specificity ; Under-replication
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    Topics: Biology
    Notes: Summary Dramatic changes in the DNA composition of post-mitotic versus mitotic and germ line nuclei occur during development in different organisms. Drosophila nasutoides possesses n=4 chromosomes which were quantified with a microphotometer in females. The diploid (2 C) DNA content was 0.79 pg or 7.7×108 nucleotide pairs, calculated from brain metaphases and calibrated with hen erythrocyte nuclei. The individual elements comprised X=9%, 2=16%, 3=13%, and 4=62% of the total complement. In polytene nuclei of larval salivary glands which had undergone 11 endoreplication cycles, chromosome 4 contained only 1.55% of total Feulgen DNA. Thus, in contrast with other Drosophila genomes, where under-replicating material is dispersed to all elements, a huge quantity of non-endoreplicating DNA is restricted to a single chromosome. This permits accurate determination of the timing of under-replication in the single cell. The data presented here suggest that the schedule is tissue-specific. Larval hind gut and salivary duct nuclei begin under-replication during the first endocycle, whereas adult and larval salivary glands mainly begin during the second cycle. In Malpighian tubules the onset of selective DNA syntheses occurs during either the first or the second endocycle.
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    Development genes and evolution 195 (1986), S. 389-398 
    ISSN: 1432-041X
    Keywords: Cell lineage ; Embryogenesis ; Drosophila ; Cell marking ; Cell transplantation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A method is presented which allows the study of the progeny of single cells during Drosophila embryogenesis. Cells from various larval anlagen of donor embryos labelled with a lineage tracer are individually transplanted from defined positions into similar, or different, positions in unlabelled hosts. The clones produced by these cells can be seen in whole mounts or in sections of fixed material, when using a histochemical marker (i.e. HRP), and/or in living embryos, when using fluorescent lineage tracers. The characteristics of the clones disclose lineage parameters, such as division patterns, morphogenetic movements and differentiation. The method is especially useful for testing the respective roles of positional information and cell lineage on the commitment of progenitor cells by transplanting these cells into heterotopic positions or into hosts of different genotypes.
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    Development genes and evolution 195 (1986), S. 399-402 
    ISSN: 1432-041X
    Keywords: Gastrula ectoderm (Triturus) ; Neural differentiation ; Hepes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Ectoderm was isolated from early gastrula stages of Triturus alpestris and cultured in salt solution buffered with either bicarbonate or Hepes as the principal buffer substance. When bicarbonate was the principal buffer substance or when bicarbonate was omitted, the isolated ectoderm formed atypical epidermis. When Hepes was added as a buffer substance, neural tissue was formed in a high percentage of cases. The differentiation of neural tissue depends on the pH of the Hepes buffer. Hepes in the protonated form, which prevails at lower pH, seems to evoke neural differentiation at a much higher rate. Hepes could either enhance the NA+/H+ antiport system or it could directly bind to plasma membrane constituents. In both cases conformational changes in the plasma membrane could generate signals which finally lead to neural differentiation.
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    Development genes and evolution 195 (1986), S. 403-407 
    ISSN: 1432-041X
    Keywords: Chick blastula ; Heat shock ; Region specific gene expression ; Differentiation
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    Notes: Summary The component areas of chick blastula show differential expression of heat shock genes. The area opaca (ao), marginal zone (mz) and central area (ca) components of the epiblast display distinct quantitative and minor qualitative differences in the heat-induced and heat-repressible proteins, but are clearly different from the primary hypoblast (endoderm) in their expression of a given stress protein (hsp) as a response to heat shock. The major proteins synthesized in the component areas of epiblast in response to heat shock include hsp 18, 24, 70 and 89 Kd. Two-dimensional electrophoresis shows that each of these proteins consists of multiple charged species. The hypoblast expresses only hsp 70 Kd at non-significant levels and shows marked inhibition in the level of synthesis of heat-shock-repressible proteins. Heat shock during the blastula stage results in an increase in the size of the blastoderm and disrupts normal embryonic development. The heat shock genes provide an important molecular marker, which attests to regional specification in the chick blastula.
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    Development genes and evolution 195 (1986), S. 74-79 
    ISSN: 1432-041X
    Keywords: Echinodermata ; Glycoprotein ; Oogenesis ; Ovary
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    Topics: Biology
    Notes: Summary A high-molecular-weight glycoprotein with a sedimentation coefficient of 22.6 has been isolated and characterized from the accessory cells in the previtellogenic ovary of the echinoid Dendraster excentricus. This glycoprotein is similar to the major yolk glycoprotein of the mature egg in its electrophoretic mobility under non-denaturing conditions, high mannose-type glycan, amino acid composition, constitutive glycopeptides, and immunological determinants. Previous histological and electron microscopical analyses led to the hypothesis that vitellogenesis involves a translocation of material from the accessory cell in the ovary to the oocyte. Because of the close similarities of the accessory cell glycoprotein to the yolk glycoprotein of the mature egg, we conclude that the glycoprotein in the accessory cell is a precursor to the major glycoprotein of the egg yolk. This conclusion is further supported by our additional finding that the accessory cell of another echinoid, Strongylocentrotus purpuratus, also contains a high-molecular-weight (24 S) glycoprotein which shows similarities to the yolk glycoprotein of the mature egg in the carbohydrate moiety and the constitutive glycopeptides.
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    Development genes and evolution 195 (1986), S. 63-73 
    ISSN: 1432-041X
    Keywords: Germ line clones ; Embryonic lethals ; Segmentation in Drosophila ; Cell lethality
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    Notes: Summary Only a small fraction of the known mutations causing death to homozygous Drosophila produce gross morphological defects during embryogenesis. We have examined fourteen such loci on the X-chromosome to determine: 1) whether the requirement for their respective activities is restricted to embryogenesis; and 2) whether the embryonic phenotype in mutant embryos is affected by the dosage of wild-type alleles in the mother. For two alleles per locus germ line clones were produced during larval development by irradiating females heterozygous for the lethal mutation and a dominant female sterile (ovoD). Only one of the 14 loci (armadillo) is required during development of the germ cell to make morphologically normal eggs. Mutations at two other loci, (bazooka and Notch), allow normal oogenesis but cause major reductions in the viability of genetically normal (i.e., heterozygous) progeny. The majority of the loci (11/14) are not required in the germ line for either oogenesis or embryogenesis. However, in three cases (extradenticle, faintoid and lethal myospheroid), germ line homozygosity results in a readily detectible enhancement of embryonic phenotype over that observed in embryos derived from heterozygous mothers still possessing one wild type allele. The same six loci which show the most substantial effects on germ line homozygosity (arm, baz, N, exd, ftd and mys) also show an amelioration of the mutant phenotypes when maternal dosage is increased to wild type levels by using attached-X females. Four of these same loci (arm, baz, N and exd were cell lethal in imaginal discs.
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    Development genes and evolution 195 (1986), S. 80-83 
    ISSN: 1432-041X
    Keywords: Epiblast ; Hypoblast ; Induction ; Primitive streak ; Protein pattern ; Chick blastoderm
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    Notes: Summary Induction of the primitive streak is correlated with specific qualitative and quantitative changes in protein synthesis in the component areas of chick blastoderm. Blastoderm embryos at the initial to intermediate primitive streak stage were labeled with L-[35S] methionine. Radioactively labeled proteins separated by two-dimensional sodium dodecyl sulphate (SDS) polyacrylamide gel electrophoresis revealed differences in the number and density of spots among the component areas of the epiblast and hypoblast. Protein patterns of the area opaca, marginal zone and central area of the epiblast are very similar qualitatively but show distinct quantitative differences. A comparison between any of the component areas of the epiblast and the hypoblast in chick blastoderm embryos, however, reveals both qualitative and quantitative differences. A protein with a molecular weight of 30,000 unique to the component areas of the epiblast, and proteins with a molecular weight of 22,000 and 37,000 unique to the hypoblast are prominent and seem to be related to the initial appearance of the primitive streak.
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  • 66
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    Keywords: Cell adhesion ; Amphibian ; Neural induction ; Reaggregation
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    Notes: Summary Cell adhesion was studied during primary embryonic induction. The disaggregation rate and reaggregation patterns were analysed in the ectoderm cells of various developing Cynopus gastrulae and neurulae. The neurectoderm cells disaggregated more slowly with gastrulation, and the neural plate cells of early neurula showed a lesser capacity for disaggregation. Although no differences in reaggregation were found between dorsal and ventral ectoderm at the early gastrula stage, there were significant differences between the induced neurectoderm and the non-induced ventral epidermal cells at the late gastrula stage. Neural plate cells of the early neurula stage were seen to form a chain-like reaggregate, but the ventral epidermal cells of the same embryo formed a cluster-like spherical reaggregate. Scanning electron microscope observations of reaggregates also showed significant differences in adhesive properties between induced neurectoderm and non-induced epidermal cells. The adhesion field of the induced neurectoderm cells was smooth, differing from the distinct ridges of the non-induced epidermal cells. These results suggest that changes in the cell adhesion system, resulting in the formation of a columnar cell shape, may occur immediately after a neural-inducing action.
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    Keywords: Neural induction ; Neural plate ; Activation of masked factor
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    Notes: Summary Neural plates which are induced in the dorsal ectoderm of Triturus by the underlying mesoderm acquire, in turn, neural-inducing activity. This process is correlated with the appearance of neural-inducing activity in the microsomal fraction of the neural plate homogenate. The high-speed supernatant also acquires inducing activity after neural induction, but to a lesser extent. The experiments suggest that a masked neuralizing factor, which is already present in the ectoderm, is in part activated and exported from the inducing neural plate cells.
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    Development genes and evolution 195 (1986), S. 143-143 
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    Development genes and evolution 195 (1986), S. 133-136 
    ISSN: 1432-041X
    Keywords: Epithelium ; Biomechanics ; Elastimeter ; Adhesion ; Manduca
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    Notes: Summary We have measured the stiffness of the monolayered epithelium which underlies the integument of an insect. Hollow vesicles of this epithelium, the hypodermis, formed during culture in a medium containing ecdysone, from squares of eye crescent integument excised from the moth Manduca sexta. Spherical vesicles were deformed by suction using an elastimeter; a plot of pressure vs. deformation has a slope which indicates the stiffness. This method allows a direct determination of the stiffness in a small patch of hypodermis at various places along the organism's surface. Vesicles produced from a sequence of sites along an adhesion gradient might show a corresponding sequence of stiffnesses. However, any difference in stiffness between vesicles from dorsal vs. ventral eye crescent was obscured by a large scatter in values for stiffness. Variation in the wall thickness of vesicles, and use of a scaling method involving elastic spheres, may underlie this scatter. The mean (±SD) corrected stiffness for all trials was 5.59±2.79 dynes/cm2/μm deformation.
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    Development genes and evolution 195 (1986), S. 137-141 
    ISSN: 1432-041X
    Keywords: Mouse embryo ; Contractile ring ; Cytochalasin B
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    Notes: Summary Blastomeres isolated from two-cell mouse embryos were cultured until they started to cleave. When the cleavage furrow developed they were subjected to cytochalasin B (CB) and were studied with the electron microscope. The initial response to CB is that the furrow is more folded and microvillous than in the control. Later the blastomeres round up. The protrusions covered with abundant long microvilli are found scattered within their equatorial surface. Extraction with glycerol solution before fixation permits visualization of condensations of felt-like filamentous material in contact with the cleavage furrow during the initial response to CB and in the protrusions of rounded cells. We consider clumping of filaments in surface protrusions to be a specific response to CB treatment of the contractile ring.
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    Development genes and evolution 195 (1986), S. 145-157 
    ISSN: 1432-041X
    Keywords: Drosophila ; Cell polarity ; Limb development ; Pattern formation ; Bristle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The legs of flies from 16 different mutant strains ofDrosophila melanogaster were examined for abnormal cuticular polarities and extra joints. The strains were chosen for study because they manifest abnormal cuticular polarities in some parts of the body (10 strains) or because they have missing or defective tarsal joints (6 strains). All but three of the stocks were found to exhibit misorientations of either the bristles, hairs, or “bract-socket vectors” on the legs. The latter term denotes an imaginary vector pointing from a hairlike structure called a “bract” to the bristle socket with which it is associated. On the legs of wild-type flies nearly all such vectors point distally, as do the bristles and hairs. In the mutant flies, the most common vector misorientation is a 180° reversal. When the bract-socket vectors of adjacent bristle sites in the same bristle row point toward one another, the distance between the sites is frequently abnormally large, whereas when the vectors point in opposite directions, the interval is frequently abnormally small. This correlation is interpreted to mean that bristle cells actively repel one another via cytoplasmic extensions that are longer in the direction of the bract-socket vector than in the opposite direction. Repulsive forces of this kind may be responsible for “fine-tuning” the regularity of bristle spacing in wild-type flies. Extra tarsal joints were found in eight of the 16 strains. A ninth strain completely lacking tarsal joints appears in some cases to have an extra tibia-basitarsus joint in its tibia. Whereas the tarsi of wild-type flies contain four joints, the tarsi ofspiny legs mutant flies contain as many as eight joints. In this extreme extra-joint phenotype, four of the joints correspond to the normal wild-type joints, and there is an extra joint in every tarsal segment except the distal-most (fifth) segment. Nearly all such ectopic extra joints have inverted polarity. In other strains the extra tarsal joints are located mainly at the wild-type joint sites, and joints of this sort have wild-type polarity. The alternation of normal and inverted (extra) joints inspiny legs resembles the alternation of normal and inverted (extra) body segment boundaries in the embryonic-lethal mutantpatch, suggesting that tarsal and body segmentation may share a common patterning mechanism.
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  • 72
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    Keywords: Lectin ; Early embryonic induction ; Competence ; Receptor-mediated endocytosis
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    Notes: Summary Isolated competent amphibian ectoderm differentiates into neural (archencephalic) structures when treated with the plant lectin concanavalin A (Con A). While the inner ectoderm layer ofXenopus laevis forms brain structures after incubation with Con A, the outer ectoderm layer differentiates into ciliated epidermis only. This difference can be correlated with the pattern of Con A bound to the plasma membrane. With gold-labelled Con A it could be shown by transmission electron microscopy (TEM) that the outer ectoderm binds substantially less lectin than the inner layer. Furthermore we observed characteristic differences at the apical and basal surfaces of the cells of the same layer, i.e. on the apical cell surface of the superficial layer almost no Con A-gold could be found. In contrast, we observed a lot of gold particles on the basal cell side of the superficial layer. However, the number on both surfaces (apical and basal side of the cell) of the inner ectoderm layer was essentially higher, which could explain its biological reaction to the Con A stimulus and the differentiation into neural structures. The data presented in this paper indicate that early and late gastrula ectoderm bind similar amounts of Con A and support the view that the decrease in competence is not correlated with a loss of receptors for inducing factors. Furthermore, we describe the binding and the internalization of Con A via receptor-mediated endocytosis and the further fate of the Con A-gold-receptor complex inside the target cell.
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    Development genes and evolution 195 (1986), S. 182-185 
    ISSN: 1432-041X
    Keywords: Sex determination ; Maternal effect ; Oogenesis ; Two-dimensional protein patterns
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    Notes: Summary Sex in the monogenic blowflyChrysomya rufifacies is under the control of a germ-line autonomous maternal effect sex realizer. In order to identify the ovarian poly(A)+RNA that might be related to sex predetermination, we analysed the patterns of cell-free translation products of total poly(A)+RNA from female and male predetermined ovaries and oocytes. During vitellogenesis we observed one transient sex-linked difference in a stable pattern composed of more than 800 in vitro translated proteins. This difference, however, was no longer detectable in mature oocytes.
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    Development genes and evolution 195 (1986), S. 168-172 
    ISSN: 1432-041X
    Keywords: Neural induction ; Mesodermalization ; Amphibian embryo
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    Notes: Summary The neural-inducing activity of artificially mesodermalized ectoderm was examined. The competent ectoderm of earlyCynops gastrula was mesodermalized by being placed in contact withCarassius swimbladder. The mesodermalized ectoderm was combined with ectoderm isolated from various developmental stages of a gastrula. Neural differentiation were observed in half the combinants, even in 18 h ectoderm, which is considered to have lost its neural competence within 6 h. This indicates that mesodermalized ectoderm is capable of inducing neural tissues at the very time it comes into contact with 18 h ectoderm. From the present study, the neural-inducing activity of mesodermalized cells may possibly be closely connected to the early process of their mesodermalization.
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    Development genes and evolution 195 (1986), S. 186-192 
    ISSN: 1432-041X
    Keywords: DNA ligase ; Gene activity ; Nuclear transplantation ; Ram spermatids ; Axolotl egg
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    Topics: Biology
    Notes: Summary During animal development and gametogenesis two DNA ligases are found and successively expressed. In this study the two DNA ligases present in the axolotl egg and the two ligases present during ram sperm cell maturation were distinguished by biochemical and immunological methods. The expression of the genes for the heavy and light ram DNA ligases has been studied using transplantation of spermatid and sperm nuclei in axolotl eggs. We found that ram DNA ligases were expressed in axolotl egg cytoplasm. The exclusion phenomenon between the heavy and light form of DNA ligase is species-specific and involves a cytoplasmic mediator. In the transplanted ram germ cell nuclei the heavy ram DNA ligase expression was found to be sensitive to inhibitors of transcription while the light one was not. When mRNA was used, no exclusion process was observed and both the heavy and light enzyme expression were sensitive to cycloheximide and not to aamanitin. These results are discussed in terms of the possible stability of the gene-regulated state following nuclear transfer.
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    Development genes and evolution 195 (1986), S. 243-251 
    ISSN: 1432-041X
    Keywords: Regeneration ; Retinoid ; Histology
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    Notes: Summary Retinoids induce proximodistal (PD) pattern duplication in zeugopodial (lower arm or leg) regenerates of normal limbs and PD pattern duplication plus anteroposterior (AP) pattern completion in double anterior half zeugopodial regenerates. In contrast, retinoids inhibit the regeneration of double posterior half zeugopodia (Kim and Stocum, 1986). Here we describe the developmental histology of regenerating normal, double anterior half and double posterior half zeugopodia in axolotls after intraperitoneal injection of retinoic acid (RA) at the stage of initial blastema cell accumulation. In all three classes of RA-treated limbs, the accumulation of blastema cells disappeared within 3 days after injection, and dedifferentiation continued to a much more proximal extent than in controls. Subsequently, however, the developmental histology of the three limb classes was different. RA-treated double posterior limbs exhibited the histological features typical of non-regenerating limbs: the premature appearance of a thick basement membrane under the wound epidermis, formation of a thick connective tissue mat between the basement membrane and the cut ends of the stump cartilages, and failure of blastema formation. In contrast, RA-treated normal zeugopodia reformed single blastemas which grew out in a posterior or posterodorsal direction. RA-treated double anterior zeugopodia formed twin blastemas that were spatially separated to varying degrees and which grew distally. The blastemas of both these RA-treated limb types consisted of a proximal, low-density cell population that formed the girdle of the regenerate and a distal, high-density cell population that formed the free limb. In the free limb portion of the blastema, the density of the mesenchymal cell population was higher than in controls. Blastemas of RA-treated normal and double anterior zeugopodia appeared similar in size and proportions to controls at the medium bud stage, but subsequently took on the characteristics of stylopodial blastemas. These observations suggest that the extra pattern induced by RA in regenerating urodele limbs may be correlated with an increase in the number of defifferentiated cells per unit of blastema volume.
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    Development genes and evolution 195 (1986), S. 345-354 
    ISSN: 1432-041X
    Keywords: Wound healing ; Collagen ; Fibronectin ; Immunofluorescence ; Chick embryo
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Summary Spontaneous cutaneous wounds occur in avian embryos (chick, duck, quail) in various prominent parts of the body, notably the elbow, the knee and the outer face of feather buds. The frequency and size and the light and electron microscopic morphology of elbow wounds in the chick embryo are described. The cutaneous lesion appears in over 80% of the embryos at around 7 days of incubation, persists through 14 days, and finally heals completely at around 16 days of incubation. No trace of the wound is visible after that age. Wound healing of these spontaneous lesions was analysed with light microscopy (using indirect immunofluorescence for the localization of type I collagen, fibronectin and laminin) and electron microscopy. The main feature of the very slow healing process, as compared with the rapid cicatrization of experimental excision wounds, appears to be a continuous damage of the healing epidermis, until, finally, definitive wound closure occurs between 14 and 16 days of incubation. In the damaged region, where the epidermis is absent, the dermis exhibits an increased density of type I collagen fibres and of fibronectin. The upper face of the bare dermis is deprived of laminin. Spontaneous lesions do not occur in isolated wings explanted on the chick chorioallantoic membrane, where the wings do not become mobile and are not in contact with the amnion. The observations and explantation experiments suggest that the skin damage is caused by friction and abrasion of the bending elbow against the amnion or the amniotic fluid.
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    Insectes sociaux 33 (1986), S. 352-358 
    ISSN: 1420-9098
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    Topics: Biology
    Description / Table of Contents: Zusammenfassung Zwei neue Arten deremarginatus-Gruppe der AmeisengattungAnochetus aus den oestlichen kolumbianische Anden werden beschrieben. Einen Art,A. elegans sp.n., ist das groesste bisher bekannte Mitglied der Gattung.
    Notes: Summary Two new species ofAnochetus in theemarginatus group (A. elegans andA. vallensis) are described from the Andes of western Colombia.A. elegans is the largest species in the genus.
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    Insectes sociaux 33 (1986), S. 306-337 
    ISSN: 1420-9098
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    Description / Table of Contents: Zusammenfassung Das Phänomen der Ortstreue von Ameisen derFormica rufa Gruppe wurde analysiert im Hinblick auf die zugrundeliegenden Orientierungsreize und die Erinnerung über Perioden der Isolation und der Winterruhe. Farbmarkierte Arbeiter zeigten eine gewisse Ortstreue zu verschiedenen Teilen eines Hügelnestes, doch war das Phänomen zu schwach, um die Erhaltung der Ortstreue außerhalb des Nestes zu erklären, die in freier Natur gemessen wurde. Dasselbe gilt für kinästhetische und andere Reize, die auf der Architektur innerhalb des Nestes beruhen. Es wird gezeigt, daß Ortstreue außerhalb des Nestes auf extrem langlebiger individueller Erinnerung räumlich organisierter visueller Reize beruht. Das Engramm wird über mehrere Monate der Winterruhe bewahrt. Es kann auf indirektem Wege als Repräsentation eines Landmarken/Baumkronen-Musters identifiziert werden. In großen Freiluftarenen angestellte Versuche zeigen jedoch, daß olfaktorische Reize, die wahrscheinlich mit Duftmarkierungen des Aktionsrammes identisch sind, eine Ursache für idiosynkratische Ortstreue während der Dunkelperiode darstellen. Diese Orientierungsreize, die im allgemeinen in Gegenwart visueller Reize ausgeschaltet sind, mögen ebenfalls im Gedächtnis gespeichert werden, doch konnte ihre Erhaltung über die Winterruhe hinweg nicht bestätigt werden. Die Möglichkeit, daß die Ameisen geomagnetische Reize verwenden könnten, wurde geprüft, doch mit negativem Resultat. Die ökologischen Implikationen der Befunde werden diskutiert.
    Notes: Summary Route fidelity and site allegiance (Ortstreue) ofFormica rufa group ants are analysed with repect to orienting cues and preservation through periods of isolation or winter dormancy. Colour-marked workers showed certain site allegiance to different parts of a moundnest, but the phenomenon was too weak to explain the retention of extranidal Ortstreue measurad in nature. The same applies to kinesthetic and other cues based on intranest architecture. Evidence is presented that extranidal Ortstreue is based on long-lasting individual memory of spatially organized visual cues. The engram stored through several months of winter dormancy can be indirectly identified with a representation of landmark/canopy patterns. The experiments carried out in large openair arenas show, however, that olfactory cues, probably identical with scent markings of the home range, are a cause of idiosyncratic Ortstreue during the dark period. The latter orienting cues, which in the main are switched off in the presence of visual cues, may also be stored in the memory, but preservation through winter dormancy could not be confirmed. The possibility that the ants may use geomagnetic cues was tested, but the result was negative. The ecological implications of the findings are discussed.
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    Pure and applied geophysics 124 (1986), S. 1-2 
    ISSN: 1420-9136
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    Pure and applied geophysics 124 (1986), S. 3-30 
    ISSN: 1420-9136
    Keywords: Structural Geology ; faults ; S. E. Spain ; experimental rock mechanics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Fault rocks formed in phyllosilicate-bearing rocks formed over a wide range of environmental conditions within the Earth's crust are characterised by similar structural and microstructural features. The most striking of these are (a) P foliation, defined by the preferred alignment of phyllosilicates in a plane oblique to the direction of shear and (b) small-scale shear zones either parallel to the shear direction (Y shears) or oblique to the direction of shear but with the opposite sense of obliquity relative to the P foliation (Riedel shears, R1). The minor shear zones have the same sense of displacement as the host shear zone. The occurrence of these and other structures in clay-rich fault gouges from exceptionally well-exposed fault zones in southeastern Spain is described. The pervasive development of these flow structures throughout large volumes of fault gouge permits fault-displacement vectors to be inferred. For the region studied the movement pictures is relatively simple and is superposed on a complex network of variably oriented fault zones. The naturally produced fault-gouge structures are compared with fault gouges produced experimentally by shearing kaolinite-quartz mixtures between intact blocks over a wide range of experimental conditions. Good correspondence between their respective microstructural features was observed. Finally, attention is drawn to the fact that natural clay-bearing fault gouges are the products of deformation accompanied by very low-grade retrogressive metamorphism, and that part of the micro-structure of these rocks may be ascribed to crystallization under stress. Microstructures are described that are from long-duration experimental runs, (5 months at high temperature and in the presence of water) which go some way towards simulating these effects.
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    Pure and applied geophysics 124 (1986), S. 53-78 
    ISSN: 1420-9136
    Keywords: Cataclasis ; gouge ; self-similar ; fractal ; fracture ; faulting
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    Topics: Geosciences , Physics
    Notes: Abstract Particle-size distributions have been determined for gouge formed by the fresh fracture of granodiorite from the Sierra Nevada batholith, for Pelona schist from the San Andreas fault zone in southern California, and for Berea sandstone from Berea, Ohio, under a variety of triaxial stress states. The finer fractions of the gouge derived from granodiorite and schist are consistent with either a self-similar or a logarithmic normal distribution, whereas the gouge from sandstone is not. Sandstone gouges are texturally similar to the disaggregated protolith, with comminution limited to the polycrystalline fragments and dominantly calcite cement. All three rock types produced significantly less gouge at higher confining pressures, but only the granodiorite showed a significant reduction in particle size with increased confining pressure. Comparison with natural gouges showed that gouges in crystalline rocks from the San Andreas fault zone also tend to be described by either a self-similar or log-normal particle distribution, with a significant reduction in particle size with increased confining pressure (depth). Natural gouges formed in porous sandstone do not follow either a self-similar or a log-normal distribution. Rather, these are represented by mixed log-normal distributions. These textural characteristics are interpreted in terms of the suppression of axial microfracturing by confining pressure and the accommodation of finite strain by scale-independent comminution.
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    Pure and applied geophysics 124 (1986), S. 159-175 
    ISSN: 1420-9136
    Keywords: Breccias ; faults ; earthquakes ; mineralization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Surface-rupture patterns and aftershock distributions accompanying moderate to large shallow earthquakes reveal a residual brittle infrastructure for established crustal fault zones, the complexity of which is likely to be largely scale-invariant. In relation to such an infrastructure, continued displacement along a particular master fault may involve three dominant mechanical processes of rock brecciation: (a)attrition brecciation, from progressive frictional wear along principal slip surfaces during both seismic and aseismic sliding, (b)distributed crush brecciation, involving microfracturing over broad regions when slip on the principal slip surfaces is impeded by antidilational jogs or other obstructions, and (c)implosion brecciation, associated with the sudden creation of void space and fluid-pressure differentials at dilational fault jogs during earthquake rupture propagation. These last, high-dilation breccias are particularly favorable sites for hydrothermal mineral deposition, forming transitory low-pressure channels for the rapid passage of hydrothermal fluids. Long-lived fault zones often contain an intermingling of breccias derived from all three processes.
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  • 84
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    Pure and applied geophysics 124 (1986), S. 203-223 
    ISSN: 1420-9136
    Keywords: Pinnate ; en-echelon ; pull-apart ; push-up ; pivotal movement
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    Topics: Geosciences , Physics
    Notes: Abstract Strike-slip fault zones observed either in the field or in model experiments generally consist of several subparallel faults which make these zones complicated in geometry and kinematics. The geometry of a strike-slip fault or shear zone is dependent on arrangement (pinnate or en echelon), on step (left step or right step), and on the rank )smaller faults within larger faults) of the subparallel fault. The relations and interactions of these three factors create a variety of dynamic circumstances and tectonic settings within the strike-slip fault zones. These include pull-aparts in the release area between subparallel faults, push-ups in the jogs where the subparallel faults overlap, and pivotal movements, or rotation, of single faults along the whole fault zone. Each kind of tectonic setting is in itself characteristic, each setting consists of many subtypes, which are controlled chiefly by the geometric parameters of the subparallel faults. One of the most important phenomena revealed in the field work is two different kinds of evolution of strike-slip fault zones: one is the evolution of a zone with a tensile component, which is related to the growth of rock bridges, and the other, of one with a compressional component, which develops by the destruction of rock bridges. In this paper we discuss, on the basis of recent research on four strike-slip fault zones in China, the essential characteristics of strike-slip faults and the possible causes of the observed structural phenomena. Attention is focussed on the deformation, development, and distribution of horizontal displacements within strike-slip fault zones.
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    Pure and applied geophysics 124 (1986), S. 309-336 
    ISSN: 1420-9136
    Keywords: Earthquakes ; pseudotachylytes ; ductile instabilities
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    Topics: Geosciences , Physics
    Notes: Abstract Pseudotachylytes from a crustal scale shear zone in Central Australia have developed in a cyclical manner: once developed, an individual pseudotachylyte is deformed in a ductile manner, only to be overprinted at a later stage by a new generation of pseudotachylytes. Such cyclic generation and deformation of pseudotachylyte has been interpreted in the past as representing conditions at the brittleductile transition; a different interpretation, however, is presented here. It is proposed that psuedotachylytes and associated ultramylonites can develop entirely within the ductile regime as ductile instabilities. Such instabilities are different in nature to those previously discussed at length in the geophysical literature but are identical in principle with the instabilities that develop for velocity-weakening frictional behavior in spring-slider systems. At a given strain rate a critical temperature,T c, is defined, at which the transient work hardening equals the product of stress relaxation due to a thermal fluctuation and the heat generated by shearing. A necessary condition for ductile instability at a given strain rate is that the temperature is belowT c; then the rate of change of stress with respect to strain is negative. An additional requirement is that this rate of change exceeds, in magnitude, the effective elastic stiffness of the loading system. Ductile instabilities are marginally possible at geological strain rates in quartzites but are possible at mid-crustal temperatures in other rock types. On the basis of these observations a new interpretation is presented for the base of the seismogenic zone in crustal regions.
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    Pure and applied geophysics 124 (1986), S. 375-381 
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    Pure and applied geophysics 124 (1986), S. 471-485 
    ISSN: 1420-9136
    Keywords: Frictional sliding ; real area of contact ; normal stress
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    Topics: Geosciences , Physics
    Notes: Abstract The real area of contact during frictional sliding has been determined as a function of changing normal stress in triaxial experiments through the use of thermodyes. Utilizing the technique, described by Teufel and Logan in 1978, with saw-cut surfaces inclined 35° to the load axis, determinations were made for monolithologic sliding of Tennessee sandstone and Indiana limestone and dilithologic sliding of the same rocks. Confining pressures to 200 MPa were investigated at a constant shortening rate of 10−2 mm/sec and at room temperature. Direct measurements were made of single-asperity areas and the asperity density. The product of these measurements gives the percent area of real contact across the sliding surface. Single-asperity area and density are found to remain relatively constant during the displacement. Single-asperity areas are in the ranges of 0.4 to 6×10−2 mm2 for sandstone, 0.8 to 2×10−2 mm2 for limestone, and 0.2 to 24×10−2 mm2 for sandstone sliding against limestone. These values are smaller than the grain size of either rock. The values increase with increasing normal stress for both monolithologic and dilithologic sliding. In sandstone the asperity density increases from about 0.8 to 2.75 contacts per square millimeter in a logarithmic fashion. Monolithologic limestone has values of about 0.9 contacts per square millimeter and does not show significant change with increasing normal stress. The percent area of real contact increases in all cases, with average maximum values of 16% of the apparent area at a normal stress of 374 MPa in sandstone, 18% at 25 MPa in limestone, and 22% at 123 MPa in the dilithologic specimens. The normal stress recalculated for the real area of contact approaches the unconfined compressive strength for sandstone and limestone.
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    Pure and applied geophysics 124 (1986), S. 587-599 
    ISSN: 1420-9136
    Keywords: Brittle fracture ; shock failure ; hydraulic fracture
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    Topics: Geosciences , Physics
    Notes: Abstract The Bridgman ring experiment, in which a hard rubber ring slipped over a steel rod was observed to split when subjected to a hydrostatic confining pressure, was repeated with Pyrex glass rings. Three cases were studied, in which (a) both ring and rod were unjacketed, (b) the inner wall of the ring was sealed from the pressure medium and (c) both rod and ring were completely jacketed. In the first two cases the ring was observed to split abruptly, with a single axial crack when confining pressure reached a critical level. In the third case no abrupt failure occurred, but a number of axial cracks were found to have formed, grown stably, but not penetrated the outer wall of the ring. The first two cases are explained by hydraulic fracturing of the ring. Observations and analysis indicate that in the third case the cracks started at flaws on the inner surface of the ring and propagated outwards in a stable manner. This case, in which a tensile crack propagates in an all-around compressive stress field, provides some insight into axial cracking of rock in triaxial compression and tensile failure of rock under radial shock loading.
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    Pure and applied geophysics 124 (1986), S. 611-658 
    ISSN: 1420-9136
    Keywords: Fracture mechanics ; source modeling ; heterogeneous fault planes ; foreshocks and aftershocks ; fractals ; moment tensor solutions
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    Topics: Geosciences , Physics
    Notes: Abstract This review was prepared as an opening lecture for the International Symposium on Physics of Fracturing and Seismic Energy Release, held at the Castle of Liblice near Prague from October 28 to November 1, 1985, and organized by the Geophysical Institute of the Czechoslovak Academy of Sciences. The review attempts to classify and synthesize results of recent studies in fracture mechanics and earthquake source physics. The following topics are discussed: recent developments in fracture mechanics, earthquake source modeling, heterogeneous fault planes, foreshocks and aftershocks, faults and fractals, and moment tensor solutions. This rather broad range of topics prevents presentation of a complete list of all relevant works, though over one hundred and seventy references are cited.
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    Pure and applied geophysics 124 (1986), S. 677-692 
    ISSN: 1420-9136
    Keywords: Stress corrosion ; surface energy ; adsorption ; double torsion ; quartz
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Strength and mechanical behavior of rocks and minerals are modified by aqueous environments. This results in two effects: mechanical and chemical. The chemical effect is investigated from both a theoretical and an experimental point of view. It is shown that a thermodynamic approach leads to a satisfactory understanding of the chemical effect through an ‘extended griffith concept’. Predictions of the model have been tested using slow crack growth experiments. The experiments have been performed with a special Double Torsion apparatus which was built for this purpose. The good agreement observed between theory and experiments suggests that subcritical crack growth in rocks is controlled by adsorption onto the crack tip. This result was previously suggested by other authors (Dunning et al., 1984). However, the important consequences of the model are that (1) there should exist a threshold stress below which subcritical crack growth stops, and this threshold depends on the environment; (2) subcritical crack growth and time-dependent phenomena could take place in the crust in a stress interval which could be as high as 50% of the rupture stress.
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    Pure and applied geophysics 124 (1986), S. 731-748 
    ISSN: 1420-9136
    Keywords: Percolation ; fracture criteria ; clustering of defects ; kinetics of fracture ; amplitude spectra of acoustic and seismic activity ; predictive signs ; tensosensitivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The statistical models of earthquake focal processes covering topological, kinetic, energetic and scaling aspects of the phenomenon are considered on the basis of the percolation and reliability theories. It is shown that these models do not contradict the basic experimental data of physics of fracture and seismology. Some predictive signs are also considered.
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  • 92
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    Keywords: Fault geometry ; earthquake rupture
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    Topics: Geosciences , Physics
    Notes: Abstract Earthquake initiation and termination processes are commonly described in terms of barriers and asperities. Barriers fall into two classes: Geometric barriers are associated with places where the orientation of failure surface changes, and relaxation barriers, where stress is low because asesmic creep processes outpace tectonic loading. Geometric barriers fall into conservative and nonconservative subgroups, according to whether finite fault motion can proceed without the creation of new structures or whether it demands the creation of new faulting or void space. The multiple faulting, or ‘fragmentation’, associated with some nonconservative barriers can disrupt fault planes and form asperities. By means of selected examples it is shown that a description in terms of these barriers can help one to visualise the processes of earthquake rupture and its relation to the geological environment.
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    Pure and applied geophysics 124 (1986), S. 825-840 
    ISSN: 1420-9136
    Keywords: Physical modelling ; tensile fracturing ; shallow earthquakes ; tensile source component
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    Topics: Geosciences , Physics
    Notes: Abstract The laboratory tests carried out in studying shear and tensile seismogenic displacements occurring in compressed samples, led us to search for earthquakes with a tensile source component. To determine this component in the seismic focus, a special procedure based on the construction of radiation patterns of the combined shear-tensile type is introduced. The criteria for selecting the events produced by the combined source mechanism are listed, and their limitations are mentioned. From the seismic zones with good azimuthal distribution of stations in the world seismic network nine earthquakes which occurred in the 6-year period 1976–1981 were analyzed; for these events better agreement of the observed and theoretical patterns was found for the combined shear-tensile source mechanism than for the pure double-couple mechanism. However, the share of the tensile component was always, found to be relatively small, ranging from 1 to 13 percent of the shear component. The comparison of the two solutions (double-couple vs. combined shear/tensile) is based on the first onset signs statistics. The results obtained indicate that tensile fracturing does not play a substantial role in the total amount of released seismic energy; on the orther hand, it is expected to be more important in the creation and development of focal zone morphology from both the instantaneous and long-term point of view.
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  • 94
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    Keywords: Scattering ; attenuation ; seismic wave-speeds
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    Topics: Geosciences , Physics
    Notes: Abstract We show that the multiple scattering by small fractures of seismic waves with wavelengths long compared to the fracture size and fracture spacing is indistinguishable from multiple-scattering effects produced by ‘regular’ porosity, except for an orientation factor due to fracture alignment. The fractures reduce theP-wave andS-wave velocities and produce an effective attenuation of the coherent component of the seismic waves. The attenuation corresponds to 1000/Q of about unity for a Gaussian spectrum of fractures, and it varies with frequencyf asf 3. For a Kolmogorov spectrum of fractures of spectral index ν the attenuation is an order of magnitude or so larger and varies with frequency asf 3-v The precise degree of attenuation depends upon the matrix properties, the fracture porosity, the degree of fracture anisotropy, the type of fluid filling the fractures, and the incidence angle of the wave. For fracture porosities less than about 15% theP-wave andS-wave velocities are decreased by the order of 5–10% with a lesser dependence on the type of fluid filling the fractures (gas, oil, or brine) and with a dependence on both the degree of anisotropy and the incident angle made by the wave. The tendency of fractures to occur perpendicularly to bedding suggests that the best way to measure seismically fractured rock behavior in situ is by using the travel-time delay and reflection amplitude. As both the offset and the azimuth of receivers vary from a shot, the travel-time delay and reflection amplitude should both show an elliptical pattern of behavior—the travel-time delay in response to the varying seismic speed, and the reflection amplitude in response to angular variations in the multiple scattering. Observations of attenuation at several frequencies should permit (a) determination of the spectrum of fractures (Gaussian versus Kolmogorovian) and (b) determination of the contribution of viscous damping to the effective attenuation.
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    Pure and applied geophysics 124 (1986), S. 1107-1115 
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    Pure and applied geophysics 124 (1986), S. i 
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    Pure and applied geophysics 124 (1986), S. 711-729 
    ISSN: 1420-9136
    Keywords: Slip-softening ; instability ; asperity ; earthquake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Slip-softening instability on a vertical strike-slip fault with asperities has been analysed. The fault strength is uniform in depth, but the strength is nonuniform in the strike direction, i.e., there are asperities on the fault. These asperities and other segments of the fault have the same type of constitutive law but different peak stresses. The material surrounding the fault is represented by elastic plates, of which the top and bottom surfaces are stress-free. We use a finite element method to study the evolution of theoretical displacement, stress and strain field with a growing displacement applied at the remote plate ends. The slip and frictional stress are obtained as part of the solution. We have compared the difference of theoretical displacement, strain field and the distribution of frictional stress on the fault between unstable and stable slip. In addition, we have studied the effect of size and strength of asperities on instability, and the softening behaviour of asperities before instability. We find that (1) the failure of the fault zone may be due to either dynamic instability or rapid quasistable slip. A general characteristic of unstable mode is that slippage, on some parts of asperities increases indefinitely for a small finite increase in remote imposed displacement until, immediately before the unstable slip; (2) the size and peak strength of asperities have a large effect on instability. Reducing the size and peak strength of asperities tends to replace inertially unstable deformation with stable deformation; (3) the location with maximum acceleration during unstable slip, as the plausible nucleating seismic source, is in asperities; (4) the shapes of the changes in theoretical stress and strain at a given location, caused by the nonlinear constitutive property of the fault, are all similar whether instability, happens or not. This fact suggests that the changes of ‘peak type’ or ‘bend type’ in crustal deformation are not required for earthquake instability.
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    Pure and applied geophysics 124 (1986), S. 749-757 
    ISSN: 1420-9136
    Keywords: Energy ; continuous fracturing ; mode
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    Topics: Geosciences , Physics
    Notes: Abstract In this paper the processes of rock deformation are discussed, which are accompanied by an accumulation of defects or by continuous fracturing. The influence of fluids and of the electrical and magnetic fields is neglected. A model of fracturing, based on some energy consideration is introduced.
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    Insectes sociaux 33 (1986), S. 26-31 
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Einzelne Arbeiterinnen (Apis mellifera L.) bekannten Alters wurden mit einer gefärbten Zuckerwasserlösung gefüttert (Spenderbiene). In einem Alter von 5–8 Tagen und nach dem 30. Tag fütterten Spenderbienen signifikant weniger Zuckerwasser an eine Gruppe von 30 Empfängerbienen weiter als Bienen anderer Altersstufen. Dies zeigt sich sowohl bei der Anzahl gefütterter Empfängerbienen als auch bei der Futtermenge, die an jede einzelne gefütterte Biene weitergegeben wurde.
    Notes: Summary Individual worker bees (Apis mellifera L.) of known age (donor bees) were artificially fed with sugar syrup containing Methylene blue as a tracer dye. The donor bee was placed into a group of 30 recipient workers and the amount of transferred food was quantified. Donor bees, at the age of 5–8 days and older than 30 days, fed significantly less sugar syrup to recipient workers than bees of other ages. This was found for both the number of fed recipients, and for the amount of food received per recipient bee.
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    Insectes sociaux 33 (1986), S. 32-44 
    ISSN: 1420-9098
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    Topics: Biology
    Description / Table of Contents: Summary To complete the study of the development of the trophallactic behavior in youngCamponotus vagus worker ants, the mature workers feeding callow ones were compared to those feeding mature workers. Mature workers frequently regurgitated food to callows and never to other mature workers. Contrary to the interactions between mature workers, the antennal repertoire is not specific of the donor role: the mature donor used the same mixed repertoire as the callow receiver, combining the repertoires of donors and receivers which, are displayed between mature workers. The organization of the antennal movement series was also found to differ and its variability is greater than in interactions between mature workers. The mature donor's trophallactic behavior thus depends on whether the partner is a callow or another mature worker.
    Notes: Resume Dans le cadre de l'étude du développement du comportement trophallactique chez les jeunes ouvrières de la fourmiCamponotus vagus, le comportement de l'ouvrière âgée qui donne de la nourriture à une receveuse immature a été comparé à celui qu'elle manifeste face à une receveuse âgée. Face à une immature, les ouvrières âgées régurgitent souvent de la nourriture de façon spontanée alors que ce comportement d'offre n'est jamais manifesté face à une autre ouvrière âgée. Le répertoire antennaire n'est pas, comme dans les interactions entre ouvrières, âgées, spécifique du rôle de donneuse: face à une immature, l'ouvrière âgée donneuse utilise le même répertoire mixte que sa partenaire, combinant les répertoires de donneuse et de receveuse manifestés entre ouvrières âgées. Des différences apparaissent également au niveau de l'organisation des mouvements antennaires et de leur variabilité, qui est plus grande que dans les interactions, entre ouvrières âgées. L'ouvrière âgée se comporte donc différemment selon qu'elle donne de la nourriture à une immature ou à une ouvrière âgée.
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