T2*-Mapping of Knee Cartilage in Response to Mechanical Loading in Alpine Skiing: A Feasibility Study.

Purpose: This study intends to establish a study protocol for the quantitative magnetic resonance imaging (qMRI) measurement of biochemical changes in knee cartilage induced by mechanical stress during alpine skiing with the implementation of new spring-loaded ski binding.

Methods: The MRI-knee-scans (T2*-mapping) of four skiers using a conventional and a spring-loaded ski binding system, alternately, were acquired before and after 1 h/4 h of exposure to alpine skiing. Intrachondral T2* analysis on 60 defined regions of interest in the femorotibial knee joint (FTJ) was conducted.

FIBER: enabling flexible retrieval of electronic health records data for clinical predictive modeling.

Objectives: The development of clinical predictive models hinges upon the availability of comprehensive clinical data. Tapping into such resources requires considerable effort from clinicians, data scientists, and engineers. Specifically, these efforts are focused on data extraction and preprocessing steps required prior to modeling, including complex database queries.

Using interpretability approaches to update "black-box" clinical prediction models: an external validation study in nephrology.

Despite advances in machine learning-based clinical prediction models, only few of such models are actually deployed in clinical contexts. Among other reasons, this is due to a lack of validation studies. In this paper, we present and discuss the validation results of a machine learning model for the prediction of acute kidney injury in cardiac surgery patients initially developed on the MIMIC-III dataset when applied to an external cohort of an American research hospital.

Identification of the site on calcineurin phosphorylated by Ca2+/CaM-dependent kinase II: modification of the CaM-binding domain.

The catalytic subunit of the Ca2+/calmodulin- (CaM) dependent phosphoprotein phosphatase calcineurin (CN) was phosphorylated by an activated form of Ca2+/CaM-dependent protein kinase II (CaM-kinase II) incorporating approximately 1 mol of phosphoryl group/mol of catalytic subunit, in agreement with a value previously reported (Hashimoto et al., 1988). Cyanogen bromide cleavage of radiolabeled CN followed by peptide fractionation using reverse-phase high-performance liquid chromatography yielded a single labeled peptide that contained a phosphoserine residue.

Interleukin 3 and phorbol ester stimulate tyrosine phosphorylation of overlapping substrate proteins.

FDC-P1 is a murine myeloid cell line that requires interleukin 3 (IL3) for survival and proliferation. While the biological effects of IL3 have been well described, the biochemical mechanisms of IL3 actions have only recently been examined. We have investigated whether IL3 or PMA stimulates phosphorylation of proteins on tyrosine as well as on serine/threonine residues as previously described [(1986) Blood 68, 906-913; (1987) Biochem.

Interleukin 3 stimulation of tyrosine kinase activity in FDC-P1 cells.

Interleukin 3 stimulates the proliferation of FDC-P1, a murine myeloid cell line, however the biochemical events subsequent to binding of IL3 have only recently begun to be investigated. We have previously described the activation of protein kinase C (PK-C) and serine/threonine phosphorylation of a 68 kd protein following IL3 treatment of FDC-P1 cells. Here we have used an anti-phosphotyrosine antibody to purify proteins containing phosphotyrosine following IL3 administration to FDC-P1 cells.

Biosynthesis of the epidermal growth factor receptor: post-translational glycosylation-independent acquisition of tyrosine kinase autophosphorylation activity.

We previously showed that the epidermal growth factor (EGF) receptor in human A431 epidermoid carcinoma cells undergoes a slow post-translational modification whereby it acquires (t1/2 = 30-40 min) EGF binding capacity (Slieker, L.J., et.

Insulin and insulin-like growth factor 1 stimulate the phosphorylation on tyrosine of a 160 kDa cytosolic protein in 3T3-L1 adipocytes.

Insulin and IGF-1 (insulin-like growth factor 1) rapidly stimulate the phosphorylation on tyrosine of a 160 kDa cytosolic protein (pp160) in intact 3T3-L1 adipocytes. Half-maximal phosphorylation of pp160 is attained with either 4 nM-insulin or 20 nM-IGF-1. A semi-quantitative immunoblotting procedure using anti-phosphotyrosine antibody revealed that the insulin-stimulated 3T3-L1 adipocyte possesses approx.

Vanadate stimulation of phosphotyrosine protein levels in quiescent Nakano mouse lens cells.

Incubation of quiescent Nakano mouse lens epithelial cells with sodium orthovanadate resulted in time- and concentration-dependent stimulation of protein tyrosine phosphorylation levels in the cells. Protein tyrosine phosphorylation in the 27,000 g pellet showed a 100% stimulation by vanadate. However, upon detergent solubilization, 30% activation of basal endogenous tyrosine phosphorylation was observed but no additional increase was obtained with vanadate.

Identification of the EDTA-extractable protein in lens as calpactin I.

The EDTA-extractable protein (EEP) is a major extrinsic protein of lens membrane. The 35 kilodalton (kDa) polypeptide of the EEP cross-reacted to antibody prepared against calpactin I, a substrate for the src protein and an inhibitor of phospholipase A2. Calpactin I is also thought to play a structural role in linking cytoskeleton to membrane.

Post-translational acquisition of ligand binding- and tyrosine kinase-domain function by the epidermal growth factor and insulin receptors.

The epidermal growth factor receptor (EGFR) and insulin receptor undergo slow post-translational modification by which they acquire hormone binding and tyrosine kinase (EGFR) function. The half-time for acquisition of EGF or insulin binding activity is 30-40 min and of tyrosine kinase activity (EGFR), is 10-15 min. Tunicamycin, an inhibitor of N-linked oligosaccharide addition, blocks acquisition of both EGF and insulin binding activity.

Synthesis of epidermal growth factor receptor in human A431 cells. Glycosylation-dependent acquisition of ligand binding activity occurs post-translationally in the endoplasmic reticulum.

It was previously demonstrated that the epidermal growth factor (EGF) receptor in human A431 cells undergoes a slow post-translational modification by which it acquires EGF binding capacity (Slieker, L.J., and Lane, M.

Modulation of calcineurin phosphotyrosyl protein phosphatase activity by calmodulin and protease treatment.

Calcineurin (CN) dephosphorylated [32P] phosphotyrosyl glutamine synthetase, a model phosphoprotein substrate containing approximately 1 mol of phosphotyrosine per mol subunit. Phosphatase activity with and without calmodulin (CaM) was greatly stimulated by Mn2+; with Ca2+, even in the presence of CaM, activity was very low. CaM-stimulated phosphatase activity exhibited deactivation with time; initial rates declined markedly after 2-3 min.

Characteristics of protein tyrosine kinase activities of Y-79 retinoblastoma cells and retina.

Protein tyrosine kinase activities were determined in retina and Y-79 retinoblastoma cells. Kinase activity was associated with particulate subcellular fractions. Specific activities were similar in both retina and Y-79 cells; apparent Km values for ATP and casein were also similar.

Protein tyrosine kinase and protein phosphotyrosine phosphatase in normal and psoriatic skin.

Protein tyrosine kinase and protein phosphotyrosine phosphatase activities were measured in extracts of skin samples from patients with psoriasis. Both kinase and phosphatase activities were significantly greater in samples taken from an involved area, characterized by epidermal hyperproliferation, than from adjacent skin of normal appearance. Samples from skin of non-psoriatic individuals were indistinguishable from the normal-appearing skin of psoriatic patients.

Micrococcal nuclease cleavage of nucleotide linked to glutamine synthetase yields phosphotyrosine at the ligation site.

The activity of micrococcal nuclease was studied on a novel substrate, denatured adenylylated glutamine synthetase [L-glutamate: ammonia ligase (ADP-forming), EC 6.3.1.

Phosphotyrosine in proteins. Stability and quantification.

The acid and base stability of the phosphoryl bond of phosphotyrosine (Tyr-P) was studied using conditions for rapid and complete hydrolysis of protein peptide bonds. A method was developed for the quantification of Tyr-P in proteins using rapid base hydrolysis and an amino acid analyzer equipped with a fluorometric detection system. The recovery of [32P]Tyr-P from base digests of radiolabeled samples of phosphotyrosyl glutamine synthetase, transforming protein of Rous sarcoma virus, casein, and rabbit anti-sarcoma IgG was 80 +/- 2%.

Heart phosphofructokinase. Allosteric kinetics following affinity labeling modification of the enzyme by 8-[m-(m-fluorosulfonylbenzamido) benzylthio] adenine.

An adenine analog 8-[m-(m-fluorosulfonylbenzamido)benzylthio]adenine (FSB-adenine) reacts covalently with sheep heart phosphofructokinase. Under conditions optimal for allosteric kinetics the modified enzyme is less sensitive to inhibition by ATP and insensitive to activation by AMP, cyclic AMP, and ADP. The concentration of fructose-6-P necessary for half-maximal activity is markedly decreased, while the cooperativity to the same substrate is not changed under the same conditions.