On the relationship between Nd isotopic composition and ocean overturning circulation in idealized freshwater discharge events

Using a cost-efficient climate model, the effect of changes in overturning circulation on neodymium isotopic composition,ϵNd, is systematically examined for the first time. Idealized sequences of abrupt climate changes are induced by the application of periodic freshwater fluxes to the North Atlantic (NA) and the Southern Ocean (SO), thus mainly affecting either the formation of North Atlantic Deep Water (NADW) or Antarctic Bottom Water (AABW). Variations in ϵNd reflect weakening and strengthening of the formation of NADW and AABW, changes in ϵNdof end-members are relatively small. Relationships betweenϵNd and the strength of NADW or AABW are more pronounced for AABW than for NADW. Atlantic patterns of variations in ϵNd systematically differ between NA and SO experiments. Additionally, the signature of changes in ϵNd in the Atlantic and the Pacific is alike in NA but opposite in SO experiments. Discrimination between NA and SO experiments is therefore possible based on the Atlantic pattern of variations in ϵNd and the contrariwise behavior of ϵNd in the Atlantic and the Pacific. In further experiments we examined the effect of variations in magnitudes of particle export fluxes. Within the examined range, and although settling particles represent the only sink of Nd, their effects on ϵNd are relatively small. Our results confirm the large potential of ϵNd as a paleocirculation tracer but also indicate its limitations of quantitative reconstructions of changes in the Atlantic Meridional Ocean Circulation.

Multiple thromboembolic events in fetofetal transfusion syndrome in triplets contributing to the understanding of pathogenesis of hydranencephaly in combination with polymicrogyria

Over the last 180 years, several theories concerning the origin of hydranencephaly have been proposed with an emphasis on infectious, aplastic, and vascular etiologies. In this report, we present a case of triplets with fetofetal transfusion syndrome of which 2 fetuses (1 and 2) developed almost similar hydranencephaly, whereas the third exhibited the features of a fetus papyraceus (3). In the monochorial triamniotic placenta, multiple arteriovenous anastomoses were detected, representing a probable route for the transmission of thrombi originating from fetus 3 causing visceral lesions in fetus 2. Hydranencephaly was histologically characterized by necrosis, macrophage invasion, and endothelial proliferation. In addition, polymicrogyria was seen in fetuses 1 and 2. The combination of multiple visceral thromboembolic events and the death of fetus 3 approximately in the 11th week of gestation suggested a vascular thrombotic pathogenesis of hydranencephaly. Polymicrogyria can be considered as postmigratory laminar necrosis. Our findings contribute to the pathogenetic understanding of combined hydranencephaly and polymicrogyria.

A guide to sparkology: the taxonomy of elementary cellular Ca2+ signaling events

Since the discovery of the Ca(2+) spark as an elementary event of cellular Ca(2+) signaling almost 15 years ago, the family of newly described Ca(2+) signal entities has been ever growing. While scientists working in Ca(2+) signaling may have maintained an overview over the specifics of this nomenclature, those outside the field often make the complaint that they feel hopelessly lost. With the present review we collect and summarize systematic information on the many Ca(2+) signaling events described in a variety of tissues and cells, and we emphasize why and how each of them has its own importance. Most of these signals are taking place in the cytosol of the respective cells, but several events have been recorded from intracellular organelles as well, where they may serve their own specific functions. Finally, we also try to convey an integrated view as to why cellular microdomain signaling is of fundamental biological importance.