Microglia are the primary resident innate immune cells of the CNS. They possess branched, motile cell processes that are important for their cellular functions. To study the pathways that control microglial morphology and motility under physiological and disease conditions, it is necessary to quantify microglial morphology and motility precisely and reliably.
View Article and Find Full Text PDFMany biological processes happen on a nano- to millimeter scale and within milliseconds. Established methods such as confocal microscopy are suitable for precise 3D recordings but lack the temporal or spatial resolution to resolve fast 3D processes and require labeled samples. Multifocal imaging (MFI) allows high-speed 3D imaging but is limited by the compromise between high spatial resolution and large field-of-view (FOV), and the requirement for bright fluorescent labels.
View Article and Find Full Text PDFMammalian oocytes are enveloped by the zona pellucida (ZP), an extracellular matrix of glycoproteins. In sperm, stimulation with ZP proteins evokes a rapid Ca influx via the sperm-specific, pH-sensitive Ca channel CatSper. However, the physiological role and molecular mechanisms underlying ZP-dependent activation of CatSper are unknown.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
June 2020
Proton (H) channels are special: They select protons against other ions that are up to a millionfold more abundant. Only a few proton channels have been identified so far. Here, we identify a family of voltage-gated "pacemaker" channels, HCNL1, that are exquisitely selective for protons.
View Article and Find Full Text PDFInside the female genital tract, mammalian sperm undergo a maturation process called capacitation, which primes the sperm to navigate across the oviduct and fertilize the egg. Sperm capacitation and motility are controlled by 3',5'-cyclic adenosine monophosphate (cAMP). Here, we show that optogenetics, the control of cellular signaling by genetically encoded light-activated proteins, allows to manipulate cAMP dynamics in sperm flagella and, thereby, sperm capacitation and motility by light.
View Article and Find Full Text PDFMotile cilia, also called flagella, are found across a broad range of species; some cilia propel prokaryotes and eukaryotic cells like sperm, while cilia on epithelial surfaces create complex fluid patterns e.g., in the brain or lung.
View Article and Find Full Text PDFWe demonstrate the use of two-color digital holographic microscopy (DHM) for imaging microbiological subjects. The use of two wavelengths significantly reduces artifacts present in the reconstructed data, allowing us to image weakly-scattering objects in close proximity to strongly-scattering objects. We demonstrate this by reconstructing the shape of the flagellum of a unicellular eukaryotic parasite in close proximity to a more strongly-scattering cell body.
View Article and Find Full Text PDFSperm are propelled by bending waves traveling along their flagellum. For steering in gradients of sensory cues, sperm adjust the flagellar waveform. Symmetric and asymmetric waveforms result in straight and curved swimming paths, respectively.
View Article and Find Full Text PDFOptogenetics allows to non-invasively manipulate cellular functions with spatio-temporal precision by combining genetic engineering with the control of protein function by light. Since the discovery of channelrhodopsin has pioneered the field, the optogenetic toolkit has been ever expanding and allows now not only to control neuronal activity by light, but rather a multitude of other cellular functions. One important application that has been established in recent years is the light-dependent control of second messenger signaling.
View Article and Find Full Text PDFFertilization is exceptionally complex and, depending on the species, happens in entirely different environments. External fertilizers in aquatic habitats, like marine invertebrates or fish, release their gametes into the seawater or freshwater, whereas sperm from most internal fertilizers like mammals cross the female genital tract to make their way to the egg. Various chemical and physical cues guide sperm to the egg.
View Article and Find Full Text PDFProtamines are arginine-rich DNA-binding proteins that replace histones in elongating spermatids. This leads to hypercondensation of chromatin and ensures physiological sperm morphology, thereby protecting DNA integrity. In mice and humans, two protamines, protamine-1 (Prm1) and protamine-2 (Prm2) are expressed in a species-specific ratio.
View Article and Find Full Text PDFThe cellular messenger cAMP regulates multiple cellular functions, including signaling in cilia and flagella. The cAMP dynamics in these subcellular compartments are ill-defined. We introduce a novel FRET-based cAMP biosensor with nanomolar sensitivity that is out of reach for other sensors.
View Article and Find Full Text PDFSperm require a sense of direction to locate the egg for fertilization. They follow gradients of chemical and physical cues provided by the egg or the oviduct. However, the principles underlying three-dimensional (3D) navigation in chemical landscapes are unknown.
View Article and Find Full Text PDFContrast Media Mol Imaging
December 2013
During stroke, the reduction of blood flow leads to undersupply of oxygen and nutrients and, finally, to cell death, but also to upregulation of pro-angiogenic molecules and vascular remodeling. However, the temporal profile of vascular changes after stroke is still poorly understood. Here, we optimized steady-state contrast-enhanced magnetic resonance imaging (SSCE MRI) and followed the dynamic changes in vascular architecture for up to 4 weeks after transient middle cerebral artery occlusion (MCAO) in rats.
View Article and Find Full Text PDFUnlabelled: The hypothesis of this study was that distinct experimental glioblastoma phenotypes resembling human disease can be noninvasively distinguished at various disease stages by imaging in vivo.
Methods: Cultured spheroids from 2 human glioblastomas were implanted into the brains of nude rats. Glioblastoma growth dynamics were followed by PET using (18)F-FDG, (11)C-methyl-l-methionine ((11)C-MET), and 3'-deoxy-3'-(18)F-fluorothymidine ((18)F-FLT) and by MRI at 3-6 wk after implantation.
Purpose: Inhibition of angiogenesis has shown clinical success in patients with cancer. Thus, imaging approaches that allow for the identification of angiogenic tumors and the detection of response to anti-angiogenic treatment are of high clinical relevance.
Experimental Design: We established an in vivo magnetic resonance imaging (MRI) approach that allows us to simultaneously image tumor microvessel density and tumor vessel size in a NSCLC model in mice.