Clinical Performance of Transient Elastography With Comparison to Quantitative Magnetic Resonance Imaging, Ultrasound, and Biopsy in Children and Adolescents With Known or Suspected Fatty Liver Disease

Background: Performance of vibration-controlled transient elastography (VCTE) is inadequately validated in pediatric nonalcoholic fatty liver disease (NAFLD). We aimed to assess the technical performance of VCTE in pediatric NAFLD and define the agreement between VCTE and reference standards of imaging and/or biopsy. Methods: This prospective study recruited participants with known or suspected NAFLD who underwent a research VCTE examination (FibroScan Mini 430). Ten valid VCTE liver stiffness measurements (kPa) and controlled attenuation parameter (CAP) (dB/m) measurements were obtained for each participant. Available clinically acquired MR elastography and magnetic resonance imaging proton density fat fraction (PDFF), liver ultrasound shear wave elastography, and biopsy served as references standards. Results: Eighty-four consecutive participants were included (55 males, mean age 15.0 ± 3.5 years, mean BMI 36.6 ± 9.4 kg/m2). VCTE examinations were complete in 80/83 participants. 37/83 participants were examined with an XL probe. There was no significant correlation between CAP and PDFF [n = 16; r = 0.17 (95% confidence interval [CI]: -0.34 to 0.61), p = 0.5] or between VCTE liver stiffness and MR elastography stiffness [n = 27; r = 0.31 (95% CI: -0.07 to 0.62), p = 0.10]. For prediction of any fibrosis stage ≥1 on biopsy (n = 9/15 participants), VCTE median liver stiffness >5.1 kPA had an area under receiver operating characteristic curve of 0.52 (95% CI: 0.26-0.78) with a sensitivity of 88.9% and specificity of 16.6% (p > 0.99). Conclusions: Complete VCTE examinations could be obtained in most pediatric patients with NAFLD. Neither VCTE liver stiffness nor CAP correlated well with measures of liver fat or stiffness by established imaging modalities and biopsy.

Fertilizing potential of mouse spermatozoa cryopreserved in a medium containing whole eggs

Experiments were conducted to improve survival of mouse spermatozoa through the cryopreservation process. In the first experiment, percentages of motile spermatozoa and fertilizing capacities of spermatozoa were evaluated when mouse spermatozoa were cryopreserved using three previously reported cryopreservation media: (1) 18% raffinose in 3% skim milk; (2) Tes/Tris medium containing 25% egg yolk and 1.25% glycerol; and (3) PBS containing 18% raffinose and 1.75% glycerol, each at three different cooling rates (-3, -10, and -50 degrees C/min). Spermatozoa frozen in the skim milk/raffinose medium exhibited the highest percentage of motile spermatozoa (39%) when cells were frozen at -10 degrees C/min (P<0.05). The second experiment evaluated the effects of modifying the Tes/Tris/egg yolk medium, comparing different concentrations of egg yolk, BSA, and sodium dodecyl sulfate. Reducing egg yolk from 25% of the medium volume to 5%, increased percentages of motile spermatozoa after cryopreservation from 29 to 36% (P<0.05). Addition of 1% BSA and sodium dodecyl sulfate to medium containing 5% egg yolk further improved percentages of motile spermatozoa after freezing. In the final experiment, 20% whole egg was substituted for 5% egg yolk and 1% BSA used in previous experiments and resulted in percentages of motile spermatozoa (51%) equal to that of the skim milk-raffinose medium. However, fertility rates were higher (68%) than for spermatozoa frozen in the skim milk-raffinose medium (P < 0.05) and were comparable to the fertility rates of fresh spermatozoa (77%; P>0.05). In conclusion, freezing mouse spermatozoa in a medium containing 20% whole egg, 0.035% sodium dodecyl sulfate, and 1.25% glycerol using a cooling rate of -10 degrees C/min preserves the motility and fertilization capacity of mouse spermatozoa.

Transient inactivation of the thylakoid photosystem II light-harvesting protein kinase system and concomitant changes in intramembrane particle size during photoinhibition of Chlamydomonas reinhardtii

Light-dependent reduction of the plastoquinone pool regulates the activity of the thylakoid-bound protein kinase which phosphorylates the light harvesting chlorophyll a,b-protein complex (LHC II) and regulates energy distribution between photosystems II (PS II) and I (Staehelin, L. A., and C. J. Arntzen, 1983, J. Cell Biol., 97:1327-1337). Since reduction of plastoquinone by PS II is abolished in photoinhibited thylakoids due to loss of the secondary electron acceptor QB protein (Kyle, D. J., I. Ohad, and C. J. Arntzen, 1984, Proc. Natl. Acad. Sci. USA, 81:4070-4074), it was of interest to examine the activity of the LHC II protein kinase system during photoinhibition and recovery of PS II activity. The kinase activity was assessed both in vivo and in vitro in Chlamydomonas cells exposed to high light intensity (photoinhibition) and recovery at low light intensity. The kinase activity was progressively reduced during photoinhibition and became undetectable after 90 min. The inactive LHC II-kinase system could not be reactivated in vitro either by light or by reduction of the plastoquinone pool following addition of reduced duroquinone (TMQH2). The LHC II polypeptides were dephosphorylated in vivo when cells, prelabeled with [32P]orthophosphate before exposure to high light intensity, were transferred to photoinhibiting light in the presence of [32P]orthophosphate. In vivo recovery of the LHC II-kinase activity, elicited by the addition of TMQH2 to the assay system, did not require restoration of QB-dependent electron flow or de novo protein synthesis, either in the cytoplasm or in the chloroplast. Mild sonication of thylakoids isolated from photoinhibited cells restored the ability of the LHC II protein kinase system to be activated in vitro by addition to TMQH2. Restoration of the light-activated LHC-II kinase required recovery of QB-dependent electron flow. At the structural level, photoinhibition did not affect the ratio of grana/stroma thylakoids. A reduction of approximately 20% of the 11-17-nm intramembrane particles and an equivalent increase in the number of 6-10.5-nm particles was observed on the E-fracture faces of stacked thylakoid membranes. Similar but smaller changes were observed also on the E-fracture faces of unstacked thylakoid membranes (more 10-14-nm and less 6-9-nm particles) and P-fracture faces of stacked thylakoid membranes (more 6-8- and less 9.5-13-nm particles). All these structural changes were reversed to normal values during recovery of PS II activity.(ABSTRACT TRUNCATED AT 400 WORDS)