1,721,083 research outputs found
Temporal stability of fMRI in medetomidine-anesthetized rats
No full textMedetomidine has become a popular choice for anesthetizing rats during long-lasting sessions of blood-oxygen-level dependent (BOLD) functional magnetic resonance imaging (fMRI). Despite this, it has not yet been established how commonly reported fMRI readouts evolve over several hours of medetomidine anesthesia and how they are affected by the precise timing, dose, and route of administration. We used four different protocols of medetomidine administration to anesthetize rats for up to six hours and repeatedly evaluated somatosensory stimulus-evoked BOLD responses and resting state functional connectivity throughout. We found that the temporal evolution of fMRI readouts strongly depended on the method of administration. Protocols that combined an initial medetomidine bolus (0.05 mg/kg) together with a subsequent continuous infusion (0.1 mg/kg/h) led to temporally stable measures of stimulus-evoked activity and functional connectivity. However, when the bolus was omitted, or the dose of medetomidine lowered, the measures attenuated in a time-dependent manner. We conclude that medetomidine can sustain consistent fMRI readouts for up to six hours of anesthesia, but only with an appropriate administration protocol. This factor should be considered for the design and interpretation of future preclinical fMRI studies in rats
Imperfect magnetic field gradients in radial k‐space encoding—Quantification, correction, and parameter dependency
No full textSPIRAL MRI for in vivo lithium-7 imaging: a feasibility study in mice after oral lithium treatment
No full textAbstract
Lithium has been the frontline treatment for bipolar disorder for over 60 years. However, its mode of action and distribution in the brain is still incompletely understood. The primary isotope of lithium, lithium-7 (
7
Li), is a magnetic resonance (MR) active, spin-3/2 nucleus. However, its low MR sensitivity and the small brain size of mice make
7
Li MR imaging (MRI) difficult in preclinical research. We tested four MRI sequences (FLASH, RARE, bSSFP, and SPIRAL) on lithium-containing phantoms, and bSSFP and SPIRAL on orally lithium-treated adult C57BL/6 mice.
7
Li MR spectroscopy was acquired weekly at 9.4T to monitor the lithium uptake. The in vivo T1 relaxation time of
7
Li was estimated in four mice. 4-h SPIRAL
7
Li MRI was acquired in ten mice at a resolution of 2 × 2 × 3 mm
3
. SPIRAL MRI provided the highest signal-to-noise ratio (SNR) per unit acquisition time and the best image quality. We observed a non-homogeneous distribution of lithium in the mouse brain, with the highest concentrations in the cortex, ventricles, and basal brain regions. Almost no lithium signal was detected in the olfactory bulb and the cerebellum. We showed that in vivo
7
Li MRI in mice is feasible, although with limited spatial resolution and SNR
Manganese-Enhanced Magnetic Resonance Imaging
No full textManganese-enhanced magnetic resonance imaging (MEMRI) relies on contrasts that are due to the shortening of the T1 relaxation time of tissue water protons that become exposed to paramagnetic manganese ions. In experimental animals, the technique combines the high spatial resolution achievable by MRI with the biological information gathered by tissue-specific or functionally induced accumulations of manganese. After in vivo administration, manganese ions may enter cells via voltage-gated calcium channels. In the nervous system, manganese ions are actively transported along the axon. Based on these properties, MEMRI is increasingly used to delineate neuroanatomical structures, assess differences in functional brain activity, and unravel neuronal connectivities in both healthy animals and models of neurological disorders. Because of the cellular toxicity of manganese, a major challenge for a successful MEMRI study is to achieve the lowest possible dose for a particular biological question. Moreover, the interpretation of MEMRI findings requires a profound knowledge of the behavior of manganese in complex organ systems under physiological and pathological conditions. Starting with an overview of manganese pharmacokinetics and mechanisms of toxicity, this chapter covers experimental methods and protocols for applications in neuroscience
Deep learning-based automated segmentation of cardiac real-time MRI in non-human primates
No full textCoordination-Induced Spin-State-Switch (CISSS) in water
Full text linkWe present a non-ionic water-soluble porphyrin that does not exhibit
measurable aggregation even at high concentrations in water. The spin state of
the corresponding nickel(II) complex changes from completely diamagnetic (low-
spin) to paramagnetic (high-spin) upon addition of a strong axial ligand. This
leads to a strongly reduced NMR relaxation time of the water protons even at
low concentrations of the complex
Ever more complex: a new type of organization of reproductive organs in female Dorippe sinica Chen, 1980 (Decapoda: Brachyura: Dorippidae)
No full textIn this study a new organization of the female reproductive organs of Eubrachyura is presented after using both histology and MRI and μCT analyses to investigate the morphology and function of the female reproductive organs of Dorippe sinica Chen, 1980. The reproductive organ is composed of two parts: an ectodermal sperm site and a mesodermal ovary. The ectodermal sperm storage site incorporates a concave vagina and a seminal receptacle, which is completely lined by cuticle and is not connected to the ovary. Additionally, a cavernous body is attached to the seminal receptacle. This cavernous body can be interpreted as an important feature in the fertilization process in relation to transporting the spermatozoa out of the lumen of the seminal receptacle. Independently of the seminal receptacle, the ovary is connected to the oviduct via a single opening. The oviduct is lined by an apocrine glandular epithelium. The oviduct and the vagina open directly into the vulva. These new discoveries are compared to the known pattern of eubrachyuran female reproductive systems
Mapping of the habenulo-interpeduncular pathway in living mice using manganese-enhanced 3D MRI
No full textThis magnetic resonance imaging (MRI) study describes mapping of the habenulo-interpeduncular pathway in living mice based on manganese-induced contrast. Six hours after intracerebroventricular microinjection of MnCl2, T1-weighted 3D MRI (2.35 T) at 117 μm isotropic resolution revealed a continuous pattern of anterograde labeling from the habenula via the fasciculus retroflexus to the interpeduncular nucleus. Alternatively, the less invasive systemic administration of MnCl2 allowed for monitoring of the dynamic uptake pattern of respective neural components with even higher reproducibility across animals. Time courses covered the range from 42 min to 24 h after injection. In conclusion, manganese-enhanced MRI may open new ways for functional assessments of the habenulo-interpeduncular system in animal models with cognitive impairment
Magnetisation transfer, T1 and T2* relaxation in canine menisci of elderly dogs—an ex vivo study in stifle joints
No full textOpen-Access-Publikationsfonds 202
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