Stephan Speier

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Advanced imaging techniques have become a valuable tool in the study of complex biological processes at the cellular level in biomedical research. Here, we introduce a new technical platform for noninvasive in vivo fluorescence imaging of pancreatic islets using the anterior chamber of the eye as a natural body window. Islets transplanted into the mouse eye(More)
Insulin-dependent diabetes is a complex multifactorial disorder characterized by loss or dysfunction of β-cells. Pancreatic β-cells differ in size, glucose responsiveness, insulin secretion and precursor cell potential; understanding the mechanisms that underlie this functional heterogeneity might make it possible to develop new regenerative approaches.(More)
There is clearly a demand for an experimental platform that enables cell biology to be studied in intact vascularized and innervated tissue in vivo. This platform should allow observations of cells noninvasively and longitudinally at single-cell resolution. For this purpose, we use the anterior chamber of the mouse eye in combination with laser scanning(More)
OBJECTIVE Freshly isolated pancreatic islets contain, in contrast to cultured islets, intraislet endothelial cells (ECs), which can contribute to the formation of functional blood vessels after transplantation. We have characterized how donor islet endothelial cells (DIECs) may contribute to the revascularization rate, vascular density, and endocrine graft(More)
Studies on the cellular function of the pancreas are typically performed in vitro on its isolated functional units, the endocrine islets of Langerhans and the exocrine acini. However, these approaches are hampered by preparation-induced changes of cell physiology and the lack of an intact surrounding. We present here a detailed protocol for the preparation(More)
We studied the effect of gap junctional coupling on the excitability of beta-cells in slices of pancreas, which provide a normal environment for islet cells. The electrophysiological properties of beta-cells from mice (C57Bl/6 background) lacking the gap junction protein connexin36 (Cx36(-/-)) were compared with heterozygous (Cx36(+/-)) and wild-type(More)
The tissue-slice technique has enabled major insights into neural and neuroendocrine physiology. Our aim was to adapt this technique to study the function of the endocrine pancreas. The preparation combines an in situ approach, as in gland perfusion, with a resolution characteristic of electrophysiological studies on single cells. The membrane potential in(More)
Islet transplantation is used therapeutically in a minority of patients with type 1 diabetes. Successful outcomes are hampered by early islet beta cell loss. The adjuvant co-transplantation of mesenchymal stromal cells (MSCs) has the promise to improve islet transplant outcome. We used a syngeneic marginal islet mass transplantation model in a mouse model(More)
In pancreatic beta-cells, inhibition of K(ATP)-channels plays a pivotal role in signal transduction of glucose-induced insulin release. However, the extreme sensitivity of K(ATP)-channels to its ligand ATP as found in inside-out patches is not directly compatible with modulation of these channels at physiological [ATP](i). We studied K(ATP)-channel(More)
Cure of type 1 diabetes (T1D) by immune intervention at disease onset depends on the restoration of insulin secretion by endogenous β-cells. However, little is known about the potential of β-cell mass and function to recover after autoimmune attack ablation. Using a longitudinal in vivo imaging approach, we show how functional status and mass of β-cells(More)