Towards the natural classification of tectarioid ferns: Confirming the phylogenetic relationships of Pleocnemia and Pteridrys (eupolypods I)

The phylogenetic relationships of the two derived fern genera Pleocnemia and Pteridrys were considered ambiguous even with molecular evidence from previous studies. In the present study we determined the phylogenetic position based on five plastid DNA regions, namely atpA, atpB, rbcL, the rps4 + rps4–trnS intergenic spacer, and the trnL-F region, and an expanded taxonomic coverage including several accessions of each of the two genera. Our results showed that the monophyletic genus Pleocnemia belonged to the Dryopteridaceae and was not related to the Tectariaceae, as it had been in the past. Pleocnemia was found to be closely related to the bolbitidoid and lastreopsioid ferns. The monophyletic genus Pteridrys was found to be sister to a clade comprising Triplophyllum and Tectarias.l. Thus, the placement of this genus into Tectariaceae was confirmed. The sinus teeth, the unique similarity shared by Pleocnemia and Pteridrys, evolved independently in the two genera. Both genera appeared to have diverged from their closest extant relatives at least since the Eocene, whereas the crown group ages indicated radiation events in the Late Miocene for both genera.     

The evolution of social inbreeding mating systems in spiders: limited male mating dispersal and lack of pre‐copulatory inbreeding avoidance in a subsocial predecessor

Cooperation and group living are extremely rare in spiders and only few species are known to be permanently social. Inbreeding is a key characteristic of social spiders, resulting in high degrees of within‐colony relatedness that may foster kin‐selected benefits of cooperation. Accordingly, philopatry and regular inbreeding are suggested to play a major role in the repeated independent origins of sociality in spiders. We conducted field observations and laboratory experiments to investigate the mating system of the subsocial spider Stegodyphus tentoriicola. The species is suggested to resemble the ‘missing link’ in the transition from subsociality to permanent sociality in Stegodyphus spiders because its social period is prolonged in comparison to other subsocial species. Individuals in our two study populations were spatially clustered around maternal nests, indicating that clusters consist of family groups as found in the subsocial congener Stegodyphus lineatus. Male mating dispersal was limited and we found no obvious pre‐copulatory inbreeding avoidance, suggesting a high likelihood of mating with close kin. Rates of polygamy were low, a pattern ensuring high relatedness within broods. In combination with ecological constraints, such as high costs of dispersal, our findings are consistent with the hypothesis that the extended social period in S. tentoriicola is accompanied with adaptations that facilitate the transition towards permanent sociality. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98 , 851–859.     

Do tracheid microstructure and the presence of minute crystals link Nymphaeaceae,Cabombaceae and Hydatellaceae?

Original scanning electron microscopy (SEM) observations are presented for stems of Brasenia schreberi and Cabomba caroliniana of Cabombaceae and three species of Trithuria of Hydatellaceae. End walls of stem tracheids of Brasenia have the same peculiar microstructure that we have reported in Barclaya, Euryale, Nuphar, Nymphaea (including Ondinea) and Victoria of Nymphaeaceae. This feature unites Cabombaceae with Nymphaeaceae. The minute rhomboidal crystals on the surfaces of stellate parenchyma cells of Brasenia reported by Solereder (1906. Oxford: University Press), but not noticed since, are figured. They are like the minute crystals of the often‐mentioned astrosclereids of Nymphaeaceae. Neither of these two features has been observed in Hydatellaceae. If the absence of these two features can be confirmed, the reason may be more related to ecology, development, habit and anatomical organization than to degree of phylogenetic relationship as shown by molecular studies. Anatomical observations on the stem anatomy of Trithuria are offered on the basis of paraffin sections prepared for a paper by Cheadle & Kosakai (1975. American Journal of Botany 62: 1017–1026); that study is notable for a discrepancy between an illustration of a specialized vessel element on the one hand and tabular data indicating long scalariform perforation plates on the other. Long scalariform perforation plates are mostly found in scalariformly pitted vessels of monocots, whereas the tracheary elements of Trithuria mostly have helical or annular thickenings. We were unable to demonstrate the presence of vessels in Hydatellaceae. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 159 , 572–582.     

Diminished transmission of drug resistant HIV-1 variants with reduced replication capacity in a human transmission model

Background

Different patterns of drug resistance are observed in treated and therapy naïve HIV-1 infected populations. Especially the NRTI-related M184I/V variants, which are among the most frequently encountered mutations in treated patients, are underrepresented in the antiretroviral naïve population. M184I/V mutations are known to have a profound effect on viral replication and tend to revert over time in the new host. However it is debated whether a diminished transmission efficacy of HIV variants with a reduced replication capacity can also contribute to the observed discrepancy in genotypic patterns.As dendritic cells (DCs) play a pivotal role in HIV-1 transmission, we used a model containing primary human Langerhans cells (LCs) and DCs to compare the transmission efficacy M184 variants (HIV-M184V/I/T) to HIV wild type (HIV-WT). As control, we used HIV harboring the NNRTI mutation K103N (HIV-K103N) which has a minor effect on replication and is found at a similar prevalence in treated and untreated individuals.

Results

In comparison to HIV-WT, the HIV-M184 variants were less efficiently transmitted to CCR5⁺ Jurkat T cells by both LCs and DCs. The transmission rate of HIV-K103N was slightly reduced to HIV-WT in LCs and even higher than HIV-WT in DCs. Replication experiments in CCR5⁺ Jurkat T cells revealed no apparent differences in replication capacity between the mutant viruses and HIV-WT. However, viral replication in LCs and DCs was in concordance with the transmission results; replication by the HIV-M184 variants was lower than replication by HIV-WT, and the level of replication of HIV-K103N was intermediate for LCs and higher than HIV-WT for DCs.

Conclusions

Our data demonstrate that drug resistant M184-variants display a reduced replication capacity in LCs and DCs which directly impairs their transmission efficacy. As such, diminished transmission efficacy may contribute to the lower prevalence of drug resistant variants in therapy naive individuals.

     

SEM studies on vessels in ferns. 11. Ophioglossum

With scanning electron microscopy (SEM), the nature of metaxylem vessel elements and tracheids was examined in Ophioglossum crotalophomides, 0. pendulum subsp. falcatum , and 0. vulgatum roots and rhizomes. Vessels were identified in all species. End walls of vessel elements, which bear perforations, are like lateral wall pitting of those elements in the secondary wall framework and differ only in absence of pit membranes or presence of pit membrane remnants. Some of the perforations contain pit membrane remnants that have large pores, small porosities, or are threadlike or weblike in structure. Dimorphic perforations were found in some vessel elements of rhizomes of 0. pendulum subsp. falcatum. Tracheids are very likely present in addition to vessels in all three species. The secondary wall framework of both tracheids and vessels is basically scalariform, although deviations in pattern are present. Vessel elements of Ophiglossum are entirely comparable to those of leptosporangiate ferns.     

RAPID ALDOSTERONE-INDUCED CELL VOLUME INCREASE OF ENDOTHELIAL CELLS MEASURED BY THE ATOMIC FORCE MICROSCOPE

Atomic force microscopy (AFM) is a useful technique for imaging the surface of living cells in three dimensions. The authors applied AFM to obtain morphological information of individual cultured endothelial cells of bovine aorta under stationary and strain conditions and to simultaneously measure changes in cell volume in response to aldosterone. This mineralocorticoid hormone is known to have acute, non-genomic effects on intracellular pH, intracellular electrolytes and inositol-1,4,5-triphosphate production. In this study whether endothelial cells under tension change their volume in response to aldosterone was tested. Such changes were already shown in human leukocytes measured by Coulter counter. In contrast to leukocytes that are more or less spherical and live in suspension, endothelial cells exhibit a complex morphology and adhere to a substrate. Thus, measurements of discrete cell volume changes in endothelial cells under physiological condition is only feasible with more sophisticated techniques. By using AFM we could precisely measure the absolute cell volume of individual living endothelial cells. Before the addition of aldosterone the cell volume of mechanically stressed endothelial cells mimicking arterial blood pressure was 1827±172fl. Cell volume was found to increase by 28% 5min after hormone exposure. Twenty-five minutes later cell volume was back to normal despite the continuous presence of aldosterone in the medium. Amiloride, a blocker of the plasma membrane Na⁺/H⁺exchanger prevented the initial aldosterone-induced volume increase. Taken together, AFM disclosed a transient swelling of endothelial cells induced by the activation of an aldosterone sensitive plasma membrane Na⁺/H⁺exchanger.     

Phylogeny of the Cardiidae (Mollusca, Bivalvia): Protocardiinae, Laevicardiinae, Lahilliinae, Tulongocardiinae subfam. n. and Pleuriocardiinae subfam. n.

In a preliminary cladistic analysis of the bivalve family Cardiidae (Schneider 1992), members of the subfamilies Protocardiinae, Lahilliinae, and Laevicardiinae, plus the genus Nemocardium , were found to be the least derived taxa of cardiids. A cladistic analysis is undertaken of the genera and subgenera of these cardiid taxa, plus several Mesozoic taxa which have never been assigned to any subfamily. The Late Triassic Tulongocardium , which is placed in Tulongocardiinae subfam. n., is the sister taxon to all other cardiids. Protocardiinae is restricted to the genus Protocardia. Most other Mesozoic taxa which have been placed in the Protocardiinae are found to be members of the Lahilliinae. Nemocardium is placed in the Laevicardiinae. Incacardium, Pleuriocardia , and Dochmocardia form a monophyletic group, Pleuriocardiinae subfam. n. Pleuriocardiinae, Laevicardiinae, and the remaining members of the Cardiidae (herein informally termed "cucardiids") form a monophyletic group.     

Physiological methods to study biofilm disinfection

This report reviews the development of a rapidin situ approach to study the physiological responses of bacteria within biofilms to disinfectants. One method utilized direct viable counts (DVC) to assess the disinfection efficacy when thin biofilms were exposed to chlorine or monochloramine. Results obtained using the DVC method were one log higher than plate count (PC) estimates of the surviving population after disinfection. Other methods incorporated the use of fluorogenic stains, a cryotomy technique to yield thin (5-m) sections of biofilm communities and examination by fluorescence microscopy. The fluorogenic stains used in this approach included 5-cyano-2,3-ditolyl tetrazolium chloride (CTC), which indicates cellular electron transport activity and Rhodamine 123, which responds specifically to proton motive force. The use of these stains allowed the microscopic discrimination of physiologically active bacteria as well as heterogeneities of active cells within thicker biofilms. The results of experiments using these techniques with pure culture and binary population biofilms on stainless steel coupons indicated biocidal activity of chlorine-based disinfectants occurred initially at the bulk-fluid interface of the communities and progressed toward the substratum. This approach provided a unique opportunity to describe the spatial response of bacteria within biofilms to antimicrobial agents and address mechanisms explaining their comparative resistance to disinfection in a way that has not been possible using traditional approaches. Results obtained using this alternative approach were also consistently higher than PC data following disinfection. These observations suggest that traditional methods involving biofilm removal and bacterial enumeration by colony formation overestimate biocide efficacy. Hence the alternative approach described here more accurately indicates the ability of bacteria surviving disinfection to recover and grow as well as demonstrate spatial heterogeneities in cellular physiological activities within biofilms.