Mapping of two new markers within the smallest interval harboring the spinal muscular atrophy locus by family and radiation hybrid analysis

The locus responsible for the childhood-onset proximal spinal muscular atrophies (SMA) has recently been mapped to an area of 2–3 Mb in the region q12–13.3 of chromosome 5. We have used a series of radiation hybrids (RHs) containing distinct parts of the SMA region as defined by reference markers. A cosmid library was constructed from one RH. Thirteen clones were isolated and five of these were mapped within the SMA region. Both RH mapping and fluorescence in situ hybridization analysis showed that two clones map in the region between loci D5S125 and D5S351. One of the cosmids contains expressed sequences. Polymorphic dinucleotide repeats were identified in both clones and used for segregation analysis of key recombinant SMA families. One recombination between the SMA locus and the new marker 9Ic (D5S685) indicates that 9Ic is probably the closest distal marker. The absence of recombination between the SMA locus and marker Fc (D5S684) suggests that Fc is located close to the disease gene. These new loci should refine linkage analysis in SMA family studies and may facilitate the isolation of the disease gene.     

On the ecology of Colurellidae (Rotifera)

A material consisting of 45 colurellid rotifers from diverse waters in south and central Sweden was analyzed to reveal their relationships to their substrate. Periphytic substrates were generally preferred. Most species are obviously mobile and more or less euryecious, but a few show a predilection for bog environments. Some colurellids are euryhaline, but when inhabiting fresh water they prefer rivers and other environments with a high oxygen concentration, probably because of problems with osmoregulation.     

Effects of individual activity sequences on prey-predator models

We study the influence of the individual behaviour of animals on predator-prey models. Populations of preys and predators are divided into sub-populations corresponding to different activity classes. The animals are assumed to do many activities all day long such as searching for food of different types. The preys are more vulnerable when doing some activities during which they are very exposed to predators attacks rather than for others during which they are hidden. We study activity sequences of the animals and also the effect of a change in the average individual behaviour of the animals on Lotka-Volterra prey-predator interactions. Numerical simulations are realized for the whole sets of equations (governing the subpopulations) and are compared to the simulations of the reduced sets of equation (governing the populations). We look for the validity of the method with respect to a scaling factor which measures the differences between the two time scales associated to the fast-varying variables and to the slow-time varying global variables. It is shown that when the two time scales differ of about two orders of magnitude, the approximation is satisfying.     

On choice of substrate and habitat in bdelzoid rotifers

Information on the distributions of 77 bdelloid rotifers from diverse waters in south and central Sweden was analyzed to reveal their relationships to substrate and habitat. Only two species were reported from plankton, both in low frequency. An artificial substrate, white cotton, was utilized only by few bdelloids, mainly by species with eyes. Only one species occurred at higher frequency on the saprobic substrate Sphaerotilus. Most bdelloids prefer environments rich in oxygen, but some species may be found in soft-bottom sediments. Several species dwell preferentially in diverse habitats of bogs. Some bdelloids have an exceptionally broad ecological range, but even for these is it possible to distinguish a pattern of preference and avoidance.     

Epimeletic behavior in a free-ranging female Risso’s dolphin (Grampus griseus)

acta ethologica - Here, we describe the epimeletic behavior of an adult Risso’s dolphin towards a deceased newborn calf of the same species across several days with photographs, acoustic...     

The differential effect of N6-benzyl-adenine and N6-(Δ2-isopentenyl)-adenine on in vitro propagation of Paeonia suffruticosa Andr. is correlated with different hormone contents

Summary N⁶-benzyl-adenine (BA) enhanced phyllogenesis and axillary bud development of Paeonia suffruticosa during in vitro culture allowing good propagation while N⁶-(²isopentenyl)adenine (iP) did not. During the first five days of culture, the mitotic activity of BA-treated explants was higher than in the iP-treated ones. High BA levels were detected in the BA-treated explants, and this was correlated with the absence of or the low indole-3-acetic acid (IAA) content. The low iP levels measured in iP-treated explants were correlated with high endogenous IAA content; the new cytokinin / auxin ratio could explain the lack of axillary buds and the development of only one leaf. Abscisic acid (ABA) was detected neither in the controls nor in the cytokinin-treated explants during the first week. However, intensive restoration of ABA accumulation was observed in controls from the third week onwards. Both BA and iP-treated explants accumulated less ABA than the controls but this hormone appeared later in the BA-treated explants than in the iP-treated ones.Abbreviations ABA abscisic acid - BA N⁶-benzyl-adenine - BHT butyl-hydroxy-toluene - ELISA enzyme linked immunosorbent assay - FM fresh mass - HPLC high performance liquid chromatography - IAA indole-3-acetic acid - iP N⁶-(²-isopentenyl)adenine - MI mitotic index - 9RBA 9-ß-D-ribofuranosyl-BA - 9RiP 9-ß-Dribofuranosyl-iP - 9RZ 9-ß-D-ribofuranosyl-zeatin - Z zeatin     

Dual mechanism of laminin modulation of ecto-5′-nucleotidase activity

The myoblast cell surface activity of ecto-5′-nucleotidase was stimulated by a laminin substrate, whereas fibronectin and gelatin did not increase the AMPase activity of ecto-5′-nucleotidase. This increase was related to a higher expression of ecto-5′-nucleotidase on the surface of cells seeded on a laminin substrate, but without the mobilization of an intracellular pool of enzyme. Furthermore, laminin and its fragments E′₁ and E₈ modified the AMPase activity of the ecto-5′-nucleotidase purified from chicken striated muscle and reconstituted in liposomes. Over the range of concentrations used, intact laminin and its fragment E₈, consisting of the distal half of the long arm, stimulated the AMPase activity of ecto-5′-nucleotidase. By contrast, the large fragment derived from the short arms, designated E′₁, inhibited the AMPase activity. Furthermore, the monoclonal anti-ecto-5′-nucleotidase antibody, CG37, abolished the stimulatory effect of fragment E₈ on the AMPase activity of ecto-5′-nucleotidase but did not reverse the inhibitory effect of fragment E′₁. In conclusion, laminin stimulates the AMPase activity of ecto-5′-nucleotidase by two mechanisms: inducing the expression of ecto-5′-nucleotidase to the cell surface and direct modulation of the enzymatic activity.     

Human pluripotent stem cell-derived extracellular vesicles: From now to the future

Extracellular vesicles (EVs) are nanometric particles that enclose cell-derived bioactive molecules in a lipid bilayer and serve as intercellular communication tools. Accordingly, in various biological contexts, EVs are reported to engage in immune modulation, senescence, and cell proliferation and differentiation. Therefore, EVs could be key elements for potential off-the-shelf cell-free therapy. Little has been studied regarding EVs derived from human pluripotent stem cells (hPSC-EVs), even though hPSCs offer good opportunities for induction of tissue regeneration and unlimited proliferative ability. In this review article, we provide an overview of studies using hPSC-EVs, focusing on identifying the conditions in which the cells are cultivated for the isolation of EVs, how they are characterized, and applications already demonstrated. The topics reported in this article highlight the incipient status of the studies in the field and the significance of hPSC-EVs’ prospective applications as PSC-derived cell-free therapy products.