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Scanning Angle Interference Microscopy (SAIM)
Published in Qiu-Xing Jiang, New Techniques for Studying Biomembranes, 2020
Cristina Bertocchi, Timothy J. Rudge, Andrea Ravasio
For imaging, the silanized silicon chip is placed facing the objective with the sample (and thermal oxide) side on the glass surface of a 27-mm glass bottom dish (Iwaki) filled with aqueous buffer (i.e., PBS, PHEM, phenol red-free growth medium, etc.). A small thumbscrew (of ~1.75 g) is placed on top of the chip to keep the wafer sample surface immobilized and flat against the glass bottom (to maintain neutral buoyancy). For live-cell imaging, the microscope chamber must be kept at 37°C and supplied with CO2 (unless using a medium buffered for pH, i.e. supplemented with HEPES). SAIM requires the acquisition of a sequence of images at consecutive calibrated laser angles of incidence (raw images in Figure 4.2b). Desired laser incidence angles for image acquisition (each corresponding to a unique TIRF motor position) can be programmed as a multidimensional acquisition into acquisition software (including, but not limited to, NIS-elements, MetaMorph and µManager) to facilitate automated and rapid data acquisition. Typically, for a wafer with 500 nm oxide height, the scanning sequence can start from the left −52° till 0° and then to the right + 52° with 4° increments or only in one direction to avoid redundancies. Nevertheless, the optimal range of angles and step sizes should be optimized according to the expected sample height above the substrate. This requires a trade-off between rate and range, because it should permit full sampling of the periodic intensity profile (more frequent inversions in fluorescence intensity can be expected for higher structures). At the completion of the laser scanning sequence acquisition, the series of raw images is saved as. ND2 file, ready for conversion, processing, analysis and reconstruction. It is important to note the excitation wavelength (since the refractive index of buffer (H2O), Si, and SiO2 are wavelength-dependent), pixel size, magnification, the incidence angles and oxide thickness for each acquisition as this information will be necessary in the analysis phase. Also, to allow for comparison between measurements, all these parameters should be maintained exactly the same across different acquisitions.
First confirmation of the hypothesis that polyhydramnios causes bone maldevelopment
Published in Journal of Obstetrics and Gynaecology, 2019
Slobodan Sekulic, Branka Petkovic
We have read the article entitled ‘Foetal biometry in polyhydramnios: does femur length fall behind?’ (Ipek et al. 2016), in this article, the authors state that chronic polyhydramnios is associated with a decrease in femur length percentiles in the third trimester relative to the second trimester of gestation. This decrease in femur length is not associated with skeletal dysplasia. Intrauterine bone development is influenced by endocrine trophic factors, mechanic stress because of bone loading and hydrostatic pressure. In the first part of gestation, the foetus is fully immersed in the amniotic fluid and it is in the condition similar to a neutral buoyancy. After the foetus has outgrown the intrauterine cavity in the last trimester of gestation, it has 60–80% of its actual weight (Sekulić et al. 2005). Polyhydramnios increases the degree of the buoyant forces to which the foetus is exposed and consequently decreases the level of mechanical stress on bones. The femur is exposed to mechanical stress during leg and whole body movements. It was hypothesised that the prolonged unloading of the femur because of polyhydramnios could cause its hypoplasia and a decreased mineralisation (Sekulic et al. 2010). A decrease in the femur length percentiles in the third trimester relative to the second trimester of gestation (Ipek 2016) is the first confirmation of the proposed hypothesis. The calcaneus, tibia, femur and vertebrae are also exposed to bone loading (Sekulić et al. 2005). The same mechanism which affects the size of the femur could affect the size of all weight bearing bones. Additionally, a decreased mechanical stress on bone in polyhydramnios could be accompanied with a decreased bone mineralisation, leading to an increased incidence of bone fracture in the postnatal period. In future prospective studies, it is necessary to obtain exact data about bone condition after birth (peripheral quantitative computed tomography, ultrasound examination, bone turnover markers). The data on muscle condition in polyhydramnios in humans are missing. There are ethical issues involved in obtaining muscle tissue for analysis.
“It didn't bring back the old me but helped me on the path to the new me”: exploring posttraumatic growth in British veterans with PTSD
Published in Disability and Rehabilitation, 2022
Petra Ann Walker, Hanna Kampman
Weightlessness was inextricably intertwined with the theme of relief from physical and psychological symptoms. Neutral buoyancy, a state where you are neither floating upwards nor sinking, was connected to decreased physical stress compared to land based PA: