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The characteristics of clinical and environmental isolates of Pseudomonas aeruginosa from both hospital and community settings were analyzed in a eukaryotic virulence model employing the AX2 and X22 mutants of Dictyostelium discoideum. Thirty-one strains, including two Australian epidemic strains, of P. aeruginosa were analyzed, five from environmental sources, six from clinical sources other than cystic fibrosis (CF) patients and nineteen from CF patients' respiratory secretions. The majority of CF isolates almost uniquely supported the growth of D. discoideum. CF isolates of P. aeruginosa were found to be less virulent than isolates from other sources. Varying degrees of inhibition of the developmental cycle of D. discoideum when growing on CF isolates were also noted. This is the first description of P. aeruginosa isolates from clinical and environmental sources supporting the growth of D. discoideum.

Le recrutement familial (pere et fils, groupe de freres) des equipages de peche cotiere dans l'Atlantique nord constitue une caracteristique constante. Meme si ce type de recrutement peut etre considere comme une suite de stages successifs dans un cycle de developpement, on a porte peu d'attention a l'evolution des equipages familiaux. A partir de donnees demographiques recueillies en Bretagne meridionale, l'article cherche a mettre en lumiere le developpement de ces equipages a travers le temps. L'analyse montre, plus precisement, que les raisons ‘psychologiques’ deja avancees pour rendre compte de la necessite et de la fragilite des equipages de freres sont purement illusoires: les tensions peuvent etre expliquees, de facpn complete et constante, par la simple realite de la pression economique. A constant feature of the North Atlantic inshore fisheries is the familial recruitment of the crews: father and sons or all-brother crews. Although this type of recruitment represents successive stages of a developmental cycle, little attention has been devoted to the evolutive pattern of the family-based crew. Drawing on demographic data collected during fieldwork in southern Brittany, the article seeks to enlighten the developmental reality of the family crew. The analysis reveals in particular that the ‘psychological’ reasons put forward to account for both the necessity and fragility of all-brother crews pertain to self-deception: the cruder reality of economic pressure explains tensions thoroughly and consistently.

The dynamics of development and production of Thelohanellus hovorkai (Myxozoa) were examined to investigate factors inducing haemorrhagic thelohanellosis in carp, Cyprinus carpio L. Fresh actinospores of T. hovorkai were harvested from the oligochaete alternate host, Branchiura sowerbyi, and used for infection experiments with myxosporean-free carp. Visualization of actinospores by fluorescent labelling revealed that sporoplasms penetrated the gill filaments of carp immersed in an actinospore suspension as early as 30 min post-exposure (PE). Plasmodia of T. hovorkai developed in the connective tissues of various organs and matured 3-5 weeks PE; dispersion of myxospores from degenerate plasmodia occurred 5-7 weeks PE. Challenges with a high dose of actinospores (4.5 x 10(6) spores per fish) resulted in the onset of disease, which was more easily achieved by the oral intubation of actinospores than by immersion in an actinospore suspension. Actinosporean-free B. sowerbyi were exposed to different densities of myxospores (10(4)-10(6) spores per oligochaete) and subsequently reared at different temperatures (15, 20, 25 degrees C). At 20 and 25 degrees C, actinospore releases were first detected 40-43 days PE, with multiple peaks of release (max. 7 x 10(5) actinospores day(-1)) during the next 60 days. We concluded that the developmental cycle of T. hovorkai was completed within 3-5 months at 20-25 degrees C, and that the ingestion of large numbers of actinospores orally, possibly by feeding on infected oligochaetes, resulted in a disease condition in carp.

Chlamydia trachomatis is an important human pathogen which possesses a unique bi-phasic developmental cycle. We used lightcycler methodology to quantitatively measure gene transcript levels in C. trachomatis strain L2. By measuring 16S rRNA transcript levels, we determined C. trachomatis L2 to have a generation time of approximately 3 h and an inclusion burst size of 200-300 particles. The three chlamydial sigma factor genes rpoD (sigma66), rpsD (sigma28) and rpoN (sigma54) exhibited different patterns of temporal expression. rpoD was central to early chlamydial development, whereas rpsD and rpoN were temporally expressed, coinciding with elementary body (EB) to reticulate body (RB) conversion and RB to EB conversion, respectively.

By histochemical and immunohistochemical methods, the presence of cholinergic-like molecules has previously been demonstrated in Paramecium primaurelia, and their functional role in mating-cell pairing was suggested. In this work, both true acetylcholinesterase (AchE) and butyrylcholinesterase (BuChE) activities were electrophoretically investigated, and the presence of molecules immunologically related to BuChE was checked by immunoblotting. The AchE activity, shown in the membrane protein fraction of mating-competent cells and in the cytoplasmic fraction of immature cells, is due to a 260-kDa molecular form, similar to the membrane-bound tetrameric form present in human erythrocytes. This AchE activity does not appear in either the cytoplasmic fraction of mating-competent cells or in the membrane protein fraction of immature cells. No evidence was found for the presence or the activity of BuChE-like molecules. The role of AchE in P. primaurelia developmental cycle is discussed. J. Exp. Zool. 283:102–105, 1999. © 1999 Wiley-Liss, Inc.

We demonstrate the preparation of samples of streptomycetes ( Streptomyces coeli-color, S. aureofaciens ) cultured on glass beads (balotina) for scanning electron microscopy. Themain trick of the method consists in immobilization of glass beads with low-melting agarose. Thesamples are then fixed in OsO 4 vapors followed by dehydration in vapors of absolute ethanol. Noair-to-liquid transition during the sample preparation occurs. Consequently, whole cell cycle ofstreptomycetes in the term of mycelial morphology can readily be studied by this method. Microsc.Res. Tech. 58:111–113, 2002. © 2002 Wiley-Liss, Inc. INTRODUCTION Streptomycetes ( Actinomycetes ), high G-C ratio Gbacteria, are important producers of secondary metab-olites including antibiotics, and are thus of great inter-est for molecular biology, medicine, and industry. Theyundergo a complex developmental cycle that involvesat least three distinct cell types. The morphologicalcharacterization of growing streptomycetes mycelia isvery important for a detailed characterization of theirlife cycle. Under laboratory conditions, streptomycetesare usually cultured in liquid media or on solid agarmedia. However, new lines of study of the streptomy-cetes life cycle, e.g., the streptomycetes proteomicproject, require new techniques of the laboratory culti-vation. Cultivation of streptomycetes on glass beads(balotina) has recently been developed (Li and Thomp-son, 1999; Nguyen et al., 2001). Here we describe apreparation procedure for samples of balotina-culti-vated streptomycetes mycelia for classical scanningelectron microscopy.

Scholars of the Chinese entrepreneurial ethic describe married women's primary entrepreneurial strategy as an indirect one—motivating sons to work hard for the family. Research in a community of overseas Chinese entrepreneurs, however, reveals diversity in married women's strategies. After cross-tabulating a number of variables, including family type, spatial organization, and firm size, this article concludes that firm size is the most influential factor with respect to women's strategies and roles. Its impact is explained in terms of the relationship of entrepreneurial ideology to Chinese family relationships and sex roles. [China, women, entre-preneurship, developmental cycle, sexual division of labor]

In a recently proposed hypothesis for the transmission of Myxosoma cerebralis, the causative agent of salmonid whirling disease, it was suggested that there was a developmental cycle in tubificid worms culminating in actinosporean spores, which were infective to the fish. Results are presented here which do not support the actinosporean involvement in the life cycle. On addition of M. cerebralis spores to Tubifex tubifex colonized in sterilized medium, no significant change in the prevalence of Triactinomyxon dubium (i.e. T. gyrosalmo) was found. Although it is shown that these worms are capable of ingesting M. cerebralis spores, neither hatching of the spores nor further development within the worm has been observed. Field observations on the distribution of actinosporean species show no obvious correlation between the occurrence of T. dubium and M. cerebralis.

Summary The structure, ultrastructure and the developmental cycle of the phycobionts living in the coralloid roots of various cycads growing in different Italian Botanical Gardens were studied. The phycobionts were examined in the various zones of the coralloids from the top towards the base. All the phycobionts observed have the characteristics typical of Nostoc. Eucaryotic algae, fungi or bacteria have never been observed. Nostoc present in the coralloid roots of various cycads differ from each other in the trichomes and the organization of vegetative cells and heterocysts. Three main types of phycobionts have been distinguished, each having preference for a group or species of cycad. In the coralloid roots the heterocystous phase prevails with vegetative cells and heterocysts. The latter differ from the heterocysts reported in other cyano-bacteria. Their frequency increases towards the basal parts of the coralloid roots and concomitantly they undergo changes until they become empty and stiff. Heterocysts releasing gonidia or dividing were not observed. In the sporogenous phase akinetes were not found. In the oldest coralloid roots few vegetative cells and numerous heterocysts in various stages were found.

Larvae of the microlepidopteran Bucculatrix maritima are monophagous leaf miners of the halophyte Aster tripolium. In the present investigation the life cycle of B. maritima was determined. Instars could be distinguished by a combination of data on head-capsule width, morphology and mining pattern. Five instar stages were distinguished. It was found that B. maritima has 2 discrete generations/year in the south-west Netherlands. The emergence of adult moths in June and in August marks the completion of the 2 developmental cycles. The winter probably is passed mostly in the 3rd instar stage. Observations on leaf mining in individual Aster specimens showed that older instars are mobile and penetrate young leaves of the same or a neighbouring plant. Larval density was conspicuously lower in Asters of a low lying part of the salt marsh than in Asters of a higher part of the marsh. This may be due to a difference in death risk, but it may also be related to the occurrence of Aster subpopulations with different food quality along a height gradient. Zusammenfassung Freilanduntersuchungen zum Entwicklungszyklus von Bucculatrix maritima (Stt.), ein Blattminierer der Halophyte Aster tripolium Der Lebenszyklus des Kleinschmetterlings Bucculatrix maritima, dessen Larven als monophage Blattminierer an der Halophyte Aster tripolium auftreten, wurde untersucht. Die Larvenstadien konnten mit Hilfe der Kombination der Daten: Kopfkapselbreite, Morphologie und Miniermuster unterschieden werden. Im Sudwesten der Niederlande hat B. maritima 2 getrennte Generationen/Jahr. Das Schlupfen der Motten im Juni und August markiert die Vollendung der 2 Entwicklungszyklen. Die Uberwinterung erfolgt uberwiegend im 3. Larvenstadium. Beobachtungen an einem Aster-Individuum zeigten, das die alteren Larvenstadien beweglich sind und in junge Blatter der selbigen oder in benachbarte Pflanzen eindringen. Die Larvendichte war in Aster-Pflanzen, die in tiefer gelegenen Teilen der Salzmarsch wuchsen, vergleichsweise niedriger als in Aster-Pflanzen, die in hoher gelegenen Teilen wuchsen. Die Ursache konnte in einem unterschiedlichen Mortalitatsrisiko, aber ebenso auch in einer unterschiedlichen Futterqualitat liegen, die durch das Auftreten von Subpopulationen von Aster in Abhangigkeit vom Hohengradienten bedingt sein konnte.

Summary Methods of Investigation of Antibiotic Resistance of Chlamydiae in Vitro In this paper first the various methods for testing antibiotic resistance of chlamydiae (estimation of minimum inhibitory concentration = MIC, minimum bactericidal concentration = MBC; “washed and reincubated” method) are discussed. The MIC of the antibiotic doxycyline was determined for 12 strains of Chlamydia psittaci in cell cultures and the influence of a number of factors on the test results investigated. McCoy and BGM cells were equally suited for determination of the MIC. Various amounts of protein in the medium and addition of cycloheximide did not influence the test results. For the 12 Chlamydia psittaci strains the average MIC value was 0.03μg/ml. Prolongation of incubation of the test-tubes (90 instead of 40 hours) altered results only insignificantly. The optimal time for the addition of the antibiotic to the infected cells was within the first two hours after infection. For determination of the MBC, repeated washing of the infected and treated cell cultures was paramount. Cell-associated doxycycline needed up to 48 hours to be washed out of the cells. A MBC could not be determined for the doxycycline preparation investigated (Vibravenos®, Pfitzer), since 20 μg/ml were not sufficient for the elimination of the agent from the cells, and higher amounts proved to be cytotoxic. The MBC as determined by a number of authors is questioned, because detection of mature infectious chlamydiae (elementary bodies) may not be substantiated after disintegration of the cells, due to the developmental cycle of chlamydiae. Zusammenfassung In der vorliegenden Arbeit werden zunachst die verschiedenen Methoden zur Bestimmung der Antibiotikumempfindlichkeit von Chlamydien — minimale Hemmkonzentration (MHK), minimale bakterizide Konzentration (MBK) und die “washed and reincubated” (W & R)-Methode — besprochen. Da die von verschiedenen Autoren verwendeten Untersuchungsmethoden variieren, wurden eigene Untersuchungen zur Bestimmung der MHK und MBK des Antibiotikums Doxycyclin (Vibravenos®, Fa. Pfizer) durchgefuhrt und dabei der Einflus verschiedener Faktoren auf das Versuchsergebnis ermittelt. McCoy- und BGM-Zellen sind gleichermasen fur den MHK-Test geeignet. Der Eiweisgehalt des Mediums sowie der Zusatz von Actidion hatte keinerlei Einflus auf die MHK. Die MHK fur Doxycyclin betrug fur 12 untersuchte Chl. psittaci-Stamme im Mittel 0,03μg/ml. Eine Verlangerung der Versuchszeit beeinfluste die MHK nur unwesentlich, z.T. erhdhten sich die Werte um 0,01 μg/ml. Als optimaler Zeitpunkt fur die Zugabe des Doxycyclins zur infizierten Zellkultur wurden die ersten 2 Stunden p. i. ermittelt. Zur Bestimmung der MBK erwies sich ein mehrmaliges Waschen der infizierten und antibiotisch behandelten Zellkultur als zwingend erforderlich, da zellassoziiertes Doxycyclin eine gewisse Zeit benotigt, um aus den Zellen herausgewaschen zu werden. Erst die in Anschlus daran vorgenommene Reinkubation und Passagierung fuhrt zu gesicherten Aussagen bezuglich der Bakterizidie von Antibiotika gegen Chl. psittaci. Im vorliegenden Fall konnte fur das verwendete Doxycyclinpraparat “Vibravenos®” die MBK nicht bestimmt werden, da Mengen von 20 μg/ml fur eine Eliminierung des Erregers nicht ausreichten und hohere Konzentrationen zytotoxische Effekte hervorriefen. Die minimale bakterizide Konzentration, wie sie von vielen Autoren bestimmt wird, wird in Frage gestellt, da den eigenen Untersuchungen zufolge und auch aufgrund von Literaturangaben hier der Nachweis von reifen, infektiosen Chlamydien (Elementarkorperchen) nach Aufschlus der antibiotikumbehandelten infizierten Wirtszellen unzureichend ist.

The existence of a pleomorphic development cycle is demonstrated in epitheliocystis organisms obtained from fish of the following families: Sparidae, Sparus aurata L.; Mugilidae, Liza ramada (Risso), Liza aurata (Risso) and Mugil cephalus L.; Cichlidae, Tilapia mossambica (Peters) and Tilapia aurea × nilotica; and Serranidae, Dicentrarchus labrax L. Ultrastructure of the successive developmental stages, primary long cells, intermediate long cells and small cells are described as well as the division process between stages. An additional stage, the round cell, was found in infected chloride cells. The affinities between epitheliocystis organisms and known chlamydial organisms of vertebrates and invertebrates are discussed.

Epitheliocystis infections in the gills of carp from Israel and Portugal occurred in lining epithelial cells as well as mucus and chloride cells. Ultrastructural studies of infected cells revealed several morphological forms of epitheliocystis showing the existence of a pleomorphic developmental cycle. The following stages were observed: chlamydia-like round cells (RC), non-dividing round cells (NRC) and bullet-shaped small cells (SC). All these were identical in shape to RC and SC described from epitheliocystis of other fish, The rickettsia-like cells (PLC and ILC) which occur in epitheliocystis from other fish species and produce the SC were absent in carp epitheliocystis and instead the RC were seen transforming into SC. Transformation to SC, however, occurred at any stage of the developmental process, even before the replication potential of the RC was exhausted, i.e. before reaching the NRC stage.

A new species of Dermocystidium is reported to be the causative agent of three outbreaks of gill disease in carp observed in recent years in Czechoslovakia. No other parasites or influences could be held responsible for the disease. It is suggested that at least some of gill disease of unknown aetiology in carp is due to dermocystidia, and the disease might be distributed in many regions of Europe. A description of a greater part of the developmental cycle of the species D. cyprini n.sp. Cervinka et Lom, is presented, supplemented by a discussion of other species of the genus. A summary of known facts on the host-parasite relation in these parasites is also given.

The developmental cycle of Nostoc muscorum, a nitrogen-fixing blue-green alga, is controlled by the spectral quality of illumination. Red light with peak activity at 650 mμ induces development of filaments from a nonfilamentous (aseriate) stage of the life cycle. Red-light photoinduction is reversed by simultaneous or subsequent exposure to light from a broad band in the green region of the spectrum. Photo-reversibility of the red-light induction, by green light, decays very slowly, remaining at an appreciable level for over 24 hr after the primary stimulus. Allophycocyanin is indicated to be the photoreceptor for red-light induction. One or more phyco-erythrins may operate as photoreceptors for reversal of induction. The dosage response and wavelength dependence of developmental photocontrol in Nostoc muscorum A indicate that a nonphotosynthetic mechanism is involved in both developmental photoinduction and its photor ever sal.

The blue-green alga Nostoc commune 584 displays a photocontrolled developmental cycle similar to that described for N. muscorum A by Lazaroff and Vishniac (1961). In both species white fluorescent light acts at the same stage, ragulating the development of motile trichomes from sheathed aseriate colonies. However white light blocks this step in N. commune 584, whereas the formation of motile trichomes is promoted by white light in N. muscorum A. Light-grown (aseriate) cultures in N. commune 584 were used to determine the action spectra for photomorphogenesis. Green light (max 520 nm) inhbited aseriate colony breakage, and red light (max 640 nm) promoted colony breakage and the differentiation of motile trichomes. On a quantum basis green light was about 3 times more effective than red light. The morphogenetic effects of either red or green light were reversible by irradiation with the other color of light. Repeated photoreversibility was observed, and the algal culutres responded only to the color of the last irradiation in a sequence. An unidentified substance is excreted into the media of motile cultures of both N. commune 584 and N. muscorum A which promotes motility in non-motile cultures. The motility-promoting substances from both species are reciprocally active. Activity is lost when the media are autoclaved.

This study focuses on the changes in house-hold composition that have occurred during the past decade in four villages located on southern Andros, Bahamas. A diachronic analysis of the changes that have occurred in the Andros household is presented, using as its methodology a statistical comparison of two censuses taken seven years apart. The statistical data fail to confirm the “typical” Andros developmental cycle, which had been derived from adult life histories (the historical method) and from frequency distributions of household types at one point in time (the cross-sectional method). The existence of many different possible household cycles probably explains this failure.

The life cycle of the spider Thomisus onustus, with its two adult phases annually, is elucidated. Differences between males and females, in the length of the developmental period up to maturity, excluded the possibility that siblings could mate in nature. Females maintain a stable cycle of one year, whereas the males show a change in the length of their developmental cycle, according to the phase from which they originate. The variance which occurs among spiderlings, in regard to the number of moults and the length of the different instars is discussed. Outlines for a general classification of the life histories of spiders is being suggested.

SYNOPSIS. The leech, Erpobdella sp., is a suitable invertebrate host for Trypanosoma ambystomae. The developmental cycle involves a mononucleate, rounded body derived from the bloodstream form; this body then transforms into a large plump crithidia. Subsequent divisions yield medium crithidia, small crithidia, and ultimately, metacyclic trypanosomes.