Caveolae in Rabbit Ventricular Myocytes: Distribution and Dynamic Diminution after Cell Isolation

Caveolae are signal transduction centers, yet their subcellular distribution and preservation in cardiac myocytes after cell isolation are not well documented. Here, we quantify caveolae located within 100 nm of the outer cell surface membrane in rabbit single-ventricular cardiomyocytes over 8 h post-isolation and relate this to the presence of caveolae in intact tissue. Hearts from New Zealand white rabbits were either chemically fixed by coronary perfusion or enzymatically digested to isolate ventricular myocytes, which were subsequently fixed at 0, 3, and 8 h post-isolation. In live cells, the patch-clamp technique was used to measure whole-cell plasma membrane capacitance, and in fixed cells, caveolae were quantified by transmission electron microscopy. Changes in cell-surface topology were assessed using scanning electron microscopy. In fixed ventricular myocardium, dual-axis electron tomography was used for three-dimensional reconstruction and analysis of caveolae in situ. The presence and distribution of surface-sarcolemmal caveolae in freshly isolated cells matches that of intact myocardium. With time, the number of surface-sarcolemmal caveolae decreases in isolated cardiomyocytes. This is associated with a gradual increase in whole-cell membrane capacitance. Concurrently, there is a significant increase in area, diameter, and circularity of sub-sarcolemmal mitochondria, indicative of swelling. In addition, electron tomography data from intact heart illustrate the regular presence of caveolae not only at the surface sarcolemma, but also on transverse-tubular membranes in ventricular myocardium. Thus, caveolae are dynamic structures, present both at surface-sarcolemmal and transverse-tubular membranes. After cell isolation, the number of surface-sarcolemmal caveolae decreases significantly within a time frame relevant for single-cell research. The concurrent increase in cell capacitance suggests that membrane incorporation of surface-sarcolemmal caveolae underlies this, but internalization and/or micro-vesicle loss to the extracellular space may also contribute. Given that much of the research into cardiac caveolae-dependent signaling utilizes isolated cells, and since caveolae-dependent pathways matter for a wide range of other study targets, analysis of isolated cell data should take the time post-isolation into account

The C-terminal region of Trypanosoma cruzi MASPs is antigenic and secreted via exovesicles.

Trypanosoma cruzi is the etiological agent of Chagas disease, a neglected and emerging tropical disease, endemic to South America and present in non-endemic regions due to human migration. The MASP multigene family is specific to T. cruzi, accounting for 6% of the parasite's genome and plays a key role in immune evasion. A common feature of MASPs is the presence of two conserved regions: an N-terminal region codifying for signal peptide and a C-terminal (C-term) region, which potentially acts as GPI-addition signal peptide. Our aim was the analysis of the presence of an immune response against the MASP C-term region. We found that this region is highly conserved, released via exovesicles (EVs) and has an associated immune response as revealed by epitope affinity mapping, IFA and inhibition of the complement lysis assays. We also demonstrate the presence of a fast IgM response in Balb/c mice infected with T. cruzi. Our results reveal the presence of non-canonical secreted peptides in EVs, which can subsequently be exposed to the immune system with a potential role in evading immune system targets in the parasite

Distribution and Diet of Ivory Gulls (Pagophila eburnea) in the North Water

Ivory gulls (Pagophila eburnea, Phipps, 1774), one of the world’s least-known species, have declined throughout their range in recent years. This study describes the patterns of ivory gull use of the North Water polynya, a large polynya that occurs every year near ivory gull breeding sites on Ellesmere Island, Nunavut, Canada. We conducted at-sea surveys from Canadian icebreakers during the summers of 1997–99. In 1998, stomach contents of five ivory gulls were analyzed. We measured stable isotope ratios (d13C, d15N) of liver, muscle, feather and bone to determine how ivory gull diets vary during the year. We observed a total of 275 individuals, most of which were seen on the western side of the polynya. Flying was the predominant behavior (76% of individuals); other behaviors included sitting on ice, sitting on water, and feeding. Four juveniles were seen in August and September. Birds collected had arctic cod (Boreogadus saida) in their stomachs. Other food items included an otolith from an unidentified species of Liparid fish and two bones from a mole, presumed to be a star-nosed mole (Condylura cristata). Stable isotope results indicated that ivory gull trophic levels (TLs) were high (around TL 4 based on d15N) but varied over the season. From the three individuals whose feathers were analyzed, we conclude that differences among individuals in their winter diets or foraging locations are possible.Les mouettes blanches (Pagophila eburnea), soit l’une des espèces les moins connues dans le monde, ont enregistré un déclin à travers l’ensemble de leurs habitats ces dernières années. Cette étude décrit les habitudes des mouettes blanches dans la polynie des eaux du Nord, une grande polynie qui se développe chaque année près des sites de reproduction de mouettes blanches sur l’île Ellesmere, au Nunavut, Canada. Nous avons effectué des relevés depuis des brise-glace canadiens au cours des étés 1997 à 1999. En 1998, le contenu des estomacs de cinq mouettes blanches a été analysé. Nous avons également mesuré les ratios d’isotopes stables (d13C, d15N) dans les foies, les muscles, les plumages et les os afin de déterminer comment le régime alimentaire des mouettes blanches variait au cours de l’année. Nous avons observé 275 individus, provenant principalement du côté ouest de la Polynie. La majorité (76 %) étaient en vol. Parmi les autres comportements observés, notons la présence d’oiseaux sur la glace, d’oiseaux sur l’eau et d’oiseaux en train de se nourrir. Quatre oiseaux juvéniles ont été repérés en août et en septembre. Les oiseaux capturés avaient de la morue polaire (Boreogadus saida) dans l’estomac. Les autres aliments trouvés comprenaient un otolithe provenant d’une espèce non identifiée de poisson Liparidé, et deux os de taupe, probablement un condylure étoilé (Condylura cristata). L’analyse des isotopes stables indique que les niveaux trophiques (NT) des mouettes blanches étaient élevés (NT 4 environ en fonction de d15N), mais variaient au cours de la saison. À partir des trois individus dont les plumes ont été analysées, nous en avons conclu qu’il est possible qu’il existe des différences entre les régimes d’hiver ou les lieux de nourriture des individus