Zygospore morphology in the conjugating green alga Spirotaenia diplohelica (Streptophyta, Zygnematophyceae, Mesotaeniaceae)

Phytotaxa ◽  
2017 ◽  
Vol 329 (3) ◽  
pp. 284
Author(s):  
PETER COESEL ◽  
ANDRÉ VANHOOF ◽  
KOOS MEESTERS

The zygospore of the saccoderm desmid Spirotaenia diplohelica is described for the first time. The spore is most peculiar, for surrounded by a series of transparent, conical projections. In that feature it very much resembles the zygospore of Spirotaenia truncata. Contrary to Spirotaenia condensata and Spirotaenia obscura, no twin zygospores are produced and walls of empty gametangial cells do not solve in an early stage but tend to stick to the zygospore for some time. In view of those essentially different modes of sexual reproduction it is not to be excluded that species in the traditional genus Spirotaenia belong to different phylogenetic cladess.

Author(s):  
Т.А. Богумил

В статье предлагается концепция жизни и творческого роста В.М. Шукшина сквозь призму тезаурусного и кластерного подходов. Объяснительными «персональными моделями» для интерпретации биографического текста писателя являются кластеры Мартина Идена, Гамлета и Степана Разина. Ранее биографы и литературоведы указывали на важность этих персон для Шукшина, но разрозненно. Впервые предпринята попытка свести указанные персональные модели воедино, в целостный сюжет становления писателя в пространстве культуры. На разных этапах эволюции автора доминирует одна из указанных моделей, последовательно сменяя друг друга, но не вытесняя, а «внахлест». Ранний этап творчества, ориентированный на стратегию Мартина Идена, является попыткой «вписаться» в наличный культурный мейнстрим. Выражено это в следовании поэтике соцреализма. Второй этап подспудно начинается с реабилитации отца Шукшина в 1956 года, когда актуализируется «гамлетовский комплекс», проявляющийся в чувстве вины перед отцом, через стратегию утаивания подлинного «я», мотивы чудаковатости. Третий этап связан с личностью реального исторического лица, Степана Разина, и выражается в открытом протесте против власти. Все важные для В.М. Шукшина поведенческие модели объединены мотивом одинокого противостояния враждебному социуму и имеют трагический финал, что обусловило ранний уход писателя и порождение мифов о насильственном характере его смерти. В.М. Шукшин одновременно был фигурой неординарной и типичной, что позволило его биографии стать «персональной моделью» для последующих авторов, выходцев из сельской глубинки. The article proposes the concept of life and creative growth of V.M. Shukshin through the prism of the thesaurus and cluster approach. The explanatory "personal models" for interpreting the biographical text of the writer are clusters of Martin Eden, Hamlet and Stepan Razin. Earlier, biographers and literary critics pointed out the importance of these people for Shukshin, but it was scattered. For the first time, an attempt was made to bring these personal models together into an integral plot of the formation of the writer in the space of culture. At different stages of the writer’s evolution, one of these models dominates, successively replacing each other, but not crowding out, but “overlapping”. The early stage of creativity, focused on Martin Eden’s strategy, is an attempt to “fit in” the current cultural mainstream. This is expressed in following the poetics of socialist realism. The second stage implicitly begins with the rehabilitation of Shukshin’s father in 1956, when the “Hamletian complex” is actualized. It is manifested in a sense of guilt towards his father, the strategy of concealing the true “I”, eccentricities. The third stage is connected with the personality of a real historical person, Stepan Razin, and is expressed in an open protest against the authorities. All important for V.M. Shukshin's behavioral models are united by the motive of a lonely confrontation with a hostile society and have a tragic ending, which led to the early departure of the writer and the generation of myths about the violent nature of his death. V.M. Shukshin was an extraordinary and typical figure at the same time. That allowed his biography to become a “personal model” for subsequent authors who came from the rural outback.


1988 ◽  
Vol 90 (2) ◽  
pp. 287-293
Author(s):  
M. F. CHAU ◽  
STEPHEN F. NG

The present study further analyses the importance of postmeiotic divisional derivatives of the micronucleus in the development of the oral apparatus of Paramecium during sexual reproduction. Cell lines possessing defective micronuclei generated by laser microbeam irradiation of the micronucleus were employed. They exhibited anomalies in nuclear reorganization and stomatogenesis in the sexual cycle. During autogamy, in some cells the micronuclear cycle terminated shortly after meiosis, resulting in the loss of all postmeiotic micronuclear derivatives. Stomatogenesis became arrested at an early stage of assembly of the oral membranelles, but the old oral apparatus was resorbed as usual, leading to the production of astomatous cells at the end of the sexual cycle. Conjugation of these cell lines with normal micronucleates rescued both nucleogenesis and stomatogenesis in the defective micronucleate conjugant, primarily as a result of transfer of the male gametic nucleus from the normal conjugant to the defective-micronucleate mate. These observations demonstrate the stomatogenic significance, in particular in the initiation of oral membranelle assembly, of the gametic nuclei during sexual reproduction. The present study also suggests the possibility of micronuclear activities in the early part of the sexual cycle affecting postzygotic nucleogenesis.


2020 ◽  
Author(s):  
María A. Duque-Correa ◽  
David Goulding ◽  
Claire Cormie ◽  
Catherine Sharpe ◽  
Judit Gali Moya ◽  
...  

ABSTRACTHundreds of millions of people are infected with whipworms (Trichuris trichiura), large metazoan parasites that live in the caecum and proximal colon. Whipworms inhabit distinct multi-intracellular epithelial burrows that have been described as syncytial tunnels. However, the interactions between first-stage (L1) larvae and the host epithelia that determine parasite invasion and establishment in the syncytium remain unclear. In vivo experiments investigating these events have been severely hampered by the limited in situ accessibility to intracellular infective larvae at the bottom of the crypts of Lieberkühn, and the lack of genetic tools such as fluorescent organisms that are readily available for other pathogens but not parasitic nematodes. Moreover, cell lines, which do not mimic the complexity of the intestinal epithelium, have been unsuccessful in supporting infection by whipworm larvae. Here, we show that caecaloids grown in an open crypt-like conformation recapitulate the caecal epithelium. Using this system, we establish in vitro infections with T. muris L1 larvae for the first-time, and provide clear evidence that syncytial tunnels are formed at this early stage. We show that larval whipworms are completely intracellular but woven through multiple cells. Using the caecaloids, we are able to visualise the pathways taken by the larvae as they burrow through the epithelial cells. We also demonstrate that larvae degrade the mucus layers overlaying the epithelium, enabling them to access the cells below. We show that early syncytial tunnels are composed of enterocytes and goblet cells that are alive and actively interacting with the larvae during the first 24 h of the infection. Progression of infection results in damage to host cells and by 72 h post-infection, we show that desmosomes of cells from infected epithelium widen and some host cells appear to become liquified. Collectively, our work unravels processes mediating the intestinal epithelium invasion by whipworms and reveals new specific interactions between the host and the parasite that allow the whipworm to establish on its multi-intracellular niche. Our study demonstrates that caecaloids can be used as a relevant in vitro model to investigate the infection biology of T. muris during the early colonisation of its host.


2008 ◽  
Vol 294 (3) ◽  
pp. E568-E575 ◽  
Author(s):  
Johannes Erdmann ◽  
Bianca Kallabis ◽  
Ulrich Oppel ◽  
Oleg Sypchenko ◽  
Stefan Wagenpfeil ◽  
...  

Obesity is associated with insulin resistance and hyperinsulinemia, which is considered to be a core component in the pathophysiology of obesity-related comorbidities. As yet it is unknown whether insulin resistance and hyperinsulinemia already develop during weight gain within the normal range. In 10 healthy male subjects the effect of intentional weight gain by 2 BMI points was examined on insulin. C-peptide and glucose levels following a meal, 75 g of glucose, and a two-step hyperglycemic clamp increased plasma glucose by 1.38 and 2.75 mmol/l, respectively. Baseline insulin, C-peptide, and glucose concentrations were significantly higher after weight gain from 21.8 to 23.8 kg/m2 BMI within 41/2 mo. Calculations of insulin secretion and clearance indicate that reduced insulin clearance contributes more to post-weight gain basal hyperinsulinemia than insulin secretion. Following oral or intravenous stimulation insulin concentrations were significantly higher post-weight gain during all three test conditions, whereas C-peptide and glucose levels did not differ. Calculations of insulin secretion and clearance demonstrated that higher stimulated insulin concentrations are entirely due to clearance but not secretion. Despite significantly higher insulin levels, the rate of intravenous glucose required to maintain the defined elevation of glucose levels was either identical (1.38 mmol/l) or even significantly lower (2.75 mmol/l) following weight gain. The present study demonstrates for the first time that insulin resistance already develops during weight gain within the normal range of body weight. The associated basal and stimulated hyperinsulinemia is the result of differentiated changes of insulin secretion and clearance, respectively.


Author(s):  
David Edward Jones ◽  
Chris Snider ◽  
Lee Kent ◽  
Ben Hicks

ABSTRACTWhile extensive modelling - both physical and virtual - is imperative to develop right-first-time products, the parallel use of virtual and physical models gives rise to two interrelated issues: the lack of revision control for physical prototypes; and the need for designers to manually inspect, measure, and interpret modifications to either virtual or physical models, for subsequent update of the other. The Digital Twin paradigm addresses similar problems later in the product life-cycle, and while these digital twins, or the “twinning” process, have shown significant value, there is little work to date on their implementation in the earlier design stages. With large prospective benefits in increased product understanding, performance, and reduced design cycle time and cost, this paper explores the concept of using the Digital Twin in early design, including an introduction to digital twinning, examination of opportunities for and challenges of their implementation, a presentation of the structure of Early Stage Twins, and evaluation via two implementation cases.


2019 ◽  
Vol 201 (18) ◽  
Author(s):  
Kathryn E. Cherny ◽  
Karin Sauer

ABSTRACT The dispersion of biofilms is an active process resulting in the release of planktonic cells from the biofilm structure. While much is known about the process of dispersion cue perception and the subsequent modulation of the c-di-GMP pool, little is known about subsequent events resulting in the release of cells from the biofilm. Given that dispersion coincides with void formation and an overall erosion of the biofilm structure, we asked whether dispersion involves degradation of the biofilm matrix. Here, we focused on extracellular genomic DNA (eDNA) due to its almost universal presence in the matrix of biofilm-forming species. We identified two probable nucleases, endA and eddB, and eddA encoding a phosphatase that were significantly increased in transcript abundance in dispersed cells. However, only inactivation of endA but not eddA or eddB impaired dispersion by Pseudomonas aeruginosa biofilms in response to glutamate and nitric oxide (NO). Heterologously produced EndA was found to be secreted and active in degrading genomic DNA. While endA inactivation had little effect on biofilm formation and the presence of eDNA in biofilms, eDNA degradation upon induction of dispersion was impaired. In contrast, induction of endA expression coincided with eDNA degradation and resulted in biofilm dispersion. Thus, released cells demonstrated a hyperattaching phenotype but remained as resistant to tobramycin as biofilm cells from which they egress, indicating EndA-dispersed cells adopted some but not all of the phenotypes associated with dispersed cells. Our findings indicate for the first time a role of DNase EndA in dispersion and suggest weakening of the biofilm matrix is a requisite for biofilm dispersion. IMPORTANCE The finding that exposure to DNase I impairs biofilm formation or leads to the dispersal of early stage biofilms has led to the realization of extracellular genomic DNA (eDNA) as a structural component of the biofilm matrix. However, little is known about the contribution of intrinsic DNases to the weakening of the biofilm matrix and dispersion of established biofilms. Here, we demonstrate for the first time that nucleases are induced in dispersed Pseudomonas aeruginosa cells and are essential to the dispersion response and that degradation of matrix eDNA by endogenously produced/secreted EndA is required for P. aeruginosa biofilm dispersion. Our findings suggest that dispersing cells mediate their active release from the biofilm matrix via the induction of nucleases.


2020 ◽  
Vol 8 (2) ◽  
pp. 228 ◽  
Author(s):  
Lilibeth Arias ◽  
Paula Cardona ◽  
Martí Català ◽  
Víctor Campo-Pérez ◽  
Clara Prats ◽  
...  

Cording was the first virulence factor identified in Mycobacterium tuberculosis (Mtb). We aimed to ascertain its role in the induction of active tuberculosis (TB) in the mouse strain C3HeB/FeJ by testing the immunopathogenic capacity of the H37Rv strain. We have obtained two batches of the same strain by stopping their growth in Proskauer Beck liquid medium once the mid-log phase was reached, in the noncording Mtb (NCMtb) batch, and two days later in the cording Mtb (CMtb) batch, when cording could be detected by microscopic analysis. Mice were challenged with each batch intravenously and followed-up for 24 days. CMtb caused a significant increase in the bacillary load at an early stage post-challenge (day 17), when a granulomatous response started, generating exudative lesions characterized by neutrophilic infiltration, which promoted extracellular bacillary growth together with cording formation, as shown for the first time in vivo. In contrast, NCMtb experienced slight or no bacillary growth and lesions could barely be detected. Previous Bacillus Calmette-Guérin (BCG) vaccination or low dose aerosol (LDA) Mtb infection were able to delay the progression towards active TB after CMtb challenge. While BCG vaccination also reduced bacillary load when NCMtb was challenged, LDA did not, and its proliferative lesions experienced neutrophil infiltration. Analysis of lung cytokine and chemokine profiles points to their capacity to block the production of CXCL-1 and further amplification of IL-1β, IL-17 and neutrophilic extracellular trap formation, all of which are essential for TB progression. These data highlight the key role of cording formation in the induction of active TB.


2005 ◽  
Vol 119 (1) ◽  
pp. 82 ◽  
Author(s):  
Kathleen L. Londry ◽  
Pascal H. Badiou ◽  
Stephen E. Grasby

The chlorophycean alga Percursaria percursa (Ulvaceae, Ulvales, Chlorophyceae), typical of marine inter-tidal zones, is reported for the first time from hypersaline springs located along the north-western shore of Lake Winnipegosis in Manitoba. Although not usually found inland, P. percursa is the dominant member of microbial mat communities that thrive in shallow pools at the outlets of hypersaline springs.


2014 ◽  
Vol 13 (2) ◽  
pp. 105-134 ◽  
Author(s):  
Seth Abrutyn

AbstractThrough the first millenniumbce, religio-cultural revolutions occurred in China, Greece, Israel, and India. Commonly referred to as the Axial Age, this epoch has been identified by some scholars as period of parallel evolution in which many of the World Religions appeared for the first time and humanity was forever changed. Axial scholarship, however, remains in an early stage as many social scientists and historians question the centrality of this era in the human story, while other unsettled debates revolve around what was common across each case. The paper below considers the Axial Age from an evolutionary-institutionalist’s perspective: what was axial was (1) the first successful religio-cultural entrepreneurs in human history and, thereby, (2) the evolution of autonomous religious spheres distinct from kinship and polity. Like the Urban Revolutions that qualitatively transformed human societies 3,000 years prior, the Axial Age represents a reconfiguration of the physical, temporal, social, and symbolic space in irreversible ways.


2008 ◽  
Vol 363 (1505) ◽  
pp. 2921-2929 ◽  
Author(s):  
Carina Cunha ◽  
Ignacio Doadrio ◽  
Maria M Coelho

Polyploidy, hybridization and variation in mating systems are central issues for a deeper understanding of animal evolution. The Iberian species Squalius alburnoides represents an example combining all three phenomena. Previous studies showed that S. alburnoides populations are mainly composed of triploid and diploid hybrid forms (mainly females), and that the tetraploid forms are rare or absent. Both populations from the Douro drainage reveal a distinct scenario: tetraploid individuals represent 85.6–97.5% of the population, with no sex ratio bias observed. Based on the flow cytometry measurements of blood and spermatozoa cells, microsatellite loci and experimental crosses, we describe here, for the first time, two symmetric allotetraploid populations (CCAA) that resumed normal meiosis after undergoing intermediate processes of non-sexual reproduction to give rise to a new sexually reproducing polyploid species. Prezygotic (habitat selection and assortative mating) and postzygotic mechanisms (nonviable embryos) are responsible for the reproductive isolation from other forms of the S. alburnoides complex (e.g. CA, CAA). This example illustrates how hybrid polyploid complexes may lead to speciation.


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