Reduction of a Tetrazolium Salt in Determining Growth Activity of Yeast-Phase Histoplasma capsulatum

A colorimetric method using a tetrazolium compound, 3,4,5-dimethylthiozalil-(1 or 2),2,5-diphenyltetrazolium bromide (TTBr), was developed for studying the growth activity of yeast-phase Histoplasma capsulatum. Materials extracted in phosphate buffer, pH 7.0, from cells at different stages of growth reduced TTBr. Colorimetric changes were correlated with enzymatic activity. Under standardized conditions specified herein, the optical density of the reduced tetrazole was an index of the growth activity of the organism.     

A biometric study of some hybridizing Crataegus populations in Denmark

Crataegus curvisepala Lindm., C. laevigata (Poiret) DC. and C. monogyna Jacq. (Rosaceae) form hybrid complexes in Denmark due to introgression. C. palmstruchii Lindm. seems to be variously introgressed individuals of C. laevigata. C. eremitagensis Raunk., C. raavadensis Raunk. and C. schumacheri Raunk. apparently belong to C. curvisepala x laevigata. The delimitation between C. curvisepala x laevigata and C. laevigata x monogyna is discussed.     

On the history of nuclear matrix manifestation

The nonchromatin proteinous residue of the cell nucleus was revealed in our laboratory as early as in 1948 and then identified by light and electron microscopy as residual nucleoli,intranuclear network and nuclear envelope before 1960,This structure termed afterwards as “nuclear residue“,“nuclear skeleton“,“nuclear cage“,“nuclear carcass“etc.,was much later(in 1974) isolated,studied and entitled as “nuclear matrix“ by Berezney and Coffey,to whom the discovery of this residual structure is often wronly ascribed.The real history of nuclear matrix manifestation is reported in this paper.     

Does urbanization affect selective pressures and life‐history strategies in the common blackbird (Turdus merula L.)?

Urbanization, one of the most extreme land‐use alterations, is currently spreading, and the number of species confronting these changes is increasing. However, contradictory results of previous studies impede a clear interpretation of which selective pressure (nest predation or food limitation) is more important in urban habitats compared with natural situations, and whether birds can confront them by adjusting their life‐history strategies. We investigated life‐history syndromes of three common blackbird (Turdus merula) populations differing in their human influence (urban, rural, and woodland). We analysed daily nest predation and nestling starvation rates to assess the relative importance of these selection pressures in each habitat. Simultaneously, several life‐history traits were investigated to determine if T. merula seem adapted to their main source of selection. Food limitation was more important in the city, whereas nest predation was the most important selective force in the forest. The rural habitat was characterized by an intermediate influence of these two factors. Life‐history syndromes, as the covariation of a suite of traits, confirmed these results because T. merula seem well adapted to the main cause of selection in each habitat. Our results are consistent with urbanization imposing new challenges on birds, and that they adaptively respond to them. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 759–766.     

Spatial proximity of proteins surrounding zyxin under force-bearing conditions

Sensing physical forces is a critical first step in mechano-transduction of cells. Zyxin, a LIM domain-containing protein, is recruited to force-bearing actin filaments and is thought to repair and strengthen them. Yet, the precise force-induced protein interactions surrounding zyxin remain unclear. Using BioID analysis, we identified proximal proteins surrounding zyxin under normal and force-bearing conditions by label-free mass spectrometry analysis. Under force-bearing conditions, increased biotinylation of α-actinin 1, α-actinin 4, and AFAP1 were detected, and these proteins accumulated along force-bearing actin fibers independently from zyxin, albeit at a lower intensity than zyxin. VASP also accumulated along force-bearing actin fibers in a zyxin-dependent manner, but the biotinylation of VASP remained constant regardless of force, supporting the model of a free zyxin–VASP complex in the cytoplasm being corecruited to tensed actin fibers. In addition, ARHGAP42, a RhoA GAP, was also identified as a proximal protein of zyxin and colocalized with zyxin along contractile actin bundles. The overexpression of ARHGAP42 reduced the rate of small wound closure, a zyxin-dependent process. These results demonstrate that the application of proximal biotinylation can resolve the proximity and composition of protein complexes as a function of force, which had not been possible with traditional biochemical analysis.     

Intact caveolae are required for proper extravillous trophoblast migration and differentiation

Caveolae constitute membrane domains critical for the organization and synchronization of different signaling molecules related to numerous cell processes such as cell migration, invasion, and differentiation. Caveolin-1 (Cav-1) is the main integral membrane protein of these domains. Recently, it was found that a normal expression of aquaporin-3 (AQP3) is required for extravillous trophoblast (EVT) cell migration. Our aim was to investigate the role of caveolae in the migration, invasion, and endovascular differentiation of human EVT cells during placentation and its interaction with AQP3. EVT cells (Swan 71 cell line) were cultured in complete Dulbecco's modified Eagle's medium–nutrient mixture F12 and treated with 5 mM methyl-β-cyclodextrin (MβCD) to disrupt caveolae. We found that after MβCD treatment, Cav-1 protein was undetectable. In this condition, the ability of the cells to migrate was significantly decreased compared with the control cells, while no differences were observed in the number of invading cells and the metalloproteinases activity between control and MβCD-treated cells. Surprisingly, the disruption of caveolae significantly enhanced EVT endovascular differentiation. On the contrary, the silencing of AQP3, negatively affected tube-like formation. The theoretical analysis of the primary sequence of AQP3 protein revealed a putative Cav-1-binding site. In addition, immunoprecipitation and double immunofluorescence assays showed that AQP3 colocalized with Cav-1. These results showed that during placentation an intact caveola in EVT cells may be necessary for AQP3 and Cav-1 interaction and any perturbations might result in serious pregnancy disorders.     

Protoplasts of systemic dimorphic fungal pathogens: Histoplasma capsulatum and blastomyces dermatitidis

Summary Protoplasts have been released fromH. capsulatum in the mycelial and yeast phases and from the mycelial and incompletly converted yeast phase ofB. dermatitidis by the enzymatic action of snail digestive juice. There is great variation in the mode of protoplast formation not only between species but between the two morphological forms, particularly inH. capsulatum These studies were supported in part by grants from the American Thoracic Socicty and the United States Public Health Service National Institute of Allergy and Infectious Diseases (1-R1-AI-7520-01).     

Emerging concept of cancer as a stem cell disorder

Evidence has accumulated that malignancy arises from maturation arrest of stem cells — rather than the dedifferentiation of somatic cells. To support this notion, stem cells in contrast to somatic cells are long lived cells and thus may become the subject of accumulating mutations that are crucial for the initiation/progression of cancer. More importantly they may maintain these mutations and pass them to daughter stem cells. Cancer stem cells (CSC) that derive from transformed normal stem cells (NSC) are responsible not only for tumor initiation, but also for its re-growth and metastasis. Accumulating evidence also indicates that adult tissues may contain a population of very small embryonic like (VSEL) stem cells that may give rise to some very immature tumors e.g., pediatric sarcomas. Similar molecular mechanisms operating in NSC and CSC regulate resistance to radio-chemotherapy and promote migration/metastasis. Thus, by studying the biology of NSC we can learn more about cancer.     

Quantification of the magnification and distortion effects of a pediatric flexible video-bronchoscope

Background

Flexible video bronchoscopes, in particular the Olympus BF Type 3C160, are commonly used in pediatric respiratory medicine. There is no data on the magnification and distortion effects of these bronchoscopes yet important clinical decisions are made from the images. The aim of this study was to systematically describe the magnification and distortion of flexible bronchoscope images taken at various distances from the object.

Methods

Using images of known objects and processing these by digital video and computer programs both magnification and distortion scales were derived.

Results

Magnification changes as a linear function between 100 mm (×1) and 10 mm (×9.55) and then as an exponential function between 10 mm and 3 mm (×40) from the object. Magnification depends on the axis of orientation of the object to the optic axis or geometrical axis of the bronchoscope. Magnification also varies across the field of view with the central magnification being 39% greater than at the periphery of the field of view at 15 mm from the object. However, in the paediatric situation the diameter of the orifices is usually less than 10 mm and thus this limits the exposure to these peripheral limits of magnification reduction. Intraclass correlations for measurements and repeatability studies between instruments are very high, r = 0.96. Distortion occurs as both barrel and geometric types but both types are heterogeneous across the field of view. Distortion of geometric type ranges up to 30% at 3 mm from the object but may be as low as 5% depending on the position of the object in relation to the optic axis.

Conclusion

We conclude that the optimal working distance range is between 40 and 10 mm from the object. However the clinician should be cognisant of both variations in magnification and distortion in clinical judgements.