Upper limb movement quality measures: comparing IMUs and optical motion capture in stroke patients performing a drinking task.

Introduction: Clinical assessment of upper limb sensorimotor function post-stroke is often constrained by low sensitivity and limited information on movement quality. To address this gap, recent studies proposed a standardized instrumented drinking task, as a representative daily activity combining different components of functional arm use. Although kinematic movement quality measures for this task are well-established, and optical motion capture (OMC) has proven effective in their measurement, its clinical application remains limited. Inertial Measurement Units (IMUs) emerge as a promising low-cost and user-friendly alternative, yet their validity and clinical relevance compared to the gold standard OMC need investigation. Method: In this study, we conducted a measurement system comparison between IMUs and OMC, analyzing 15 established movement quality measures in 15 mild and moderate stroke patients performing the drinking task, using five IMUs placed on each wrist, upper arm, and trunk. Results: Our findings revealed strong agreement between the systems, with 12 out of 15 measures demonstrating clinical applicability, evidenced by Limits of Agreement (LoA) below the Minimum Clinically Important Differences (MCID) for each measure. Discussion: These results are promising, suggesting the clinical applicability of IMUs in quantifying movement quality for mildly and moderately impaired stroke patients performing the drinking task.

Automated lung cancer assessment on 18F-PET/CT using Retina U-Net and anatomical region segmentation.

OBJECTIVES: To develop and test a Retina U-Net algorithm for the detection of primary lung tumors and associated metastases of all stages on FDG-PET/CT. METHODS: A data set consisting of 364 FDG-PET/CTs of patients with histologically confirmed lung cancer was used for algorithm development and internal testing. The data set comprised tumors of all stages. All lung tumors (T), lymphatic metastases (N), and distant metastases (M) were manually segmented as 3D volumes using whole-body PET/CT series. The data set was split into a training (n = 216), validation (n = 74), and internal test data set (n = 74). Detection performance for all lesion types at multiple classifier thresholds was evaluated and false-positive-findings-per-case (FP/c) calculated. Next, detected lesions were assigned to categories T, N, or M using an automated anatomical region segmentation. Furthermore, reasons for FPs were visually assessed and analyzed. Finally, performance was tested on 20 PET/CTs from another institution. RESULTS: Sensitivity for T lesions was 86.2% (95% CI: 77.2-92.7) at a FP/c of 2.0 on the internal test set. The anatomical correlate to most FPs was the physiological activity of bone marrow (16.8%). TNM categorization based on the anatomical region approach was correct in 94.3% of lesions. Performance on the external test set confirmed the good performance of the algorithm (overall detection rate = 88.8% (95% CI: 82.5-93.5%) and FP/c = 2.7). CONCLUSIONS: Retina U-Nets are a valuable tool for tumor detection tasks on PET/CT and can form the backbone of reading assistance tools in this field. FPs have anatomical correlates that can lead the way to further algorithm improvements. The code is publicly available. KEY POINTS: • Detection of malignant lesions in PET/CT with Retina U-Net is feasible. • All false-positive findings had anatomical correlates, physiological bone marrow activity being the most prevalent. • Retina U-Nets can build the backbone for tools assisting imaging professionals in lung tumor staging.

Affinity protein-based FRET tools for cellular tracking of chitosan nanoparticles and determination of the polymer degree of acetylation.

Chitosan (CS) is a family of linear polysaccharides with diverse applications in medicine, agriculture, and industry. Its bioactive properties are determined by parameters such as the degree of acetylation (DA), but current techniques to measure the DA are laborious and require large amounts of substrate and sophisticated equipment. It is also challenging to monitor the fate of chitosan-based nanoparticles (CS-NPs) in vitro because current tools cannot measure their enzymatic or chemical degradation. We have developed a method based on the Förster resonance energy transfer (FRET) that occurs between two independent fluorescent proteins fused to a CS-binding domain, who interact with CS polymers or CS-NPs. We used this approach to calibrate a simple and rapid analytical method that can determine the DA of CS substrates. We showed unequivocally that FRET occurs on the surface of CS-NPs and that the FRET signal is quenched by enzymatic degradation of the CS substrate. Finally, we provide in vitro proof-of-concept that these approaches can be used to label CS-NPs and colocalize them following their interactions with mammalian cells.

Cholinesterases and peanut agglutinin binding related to cell proliferation and axonal growth in embryonic chick limbs.

Embryonic cholinesterases are assigned important functions during morphogenesis. Here we describe the expression of butyrylcholinesterase and acetylcholinesterase, and the binding of peanut agglutinin, and relate the results to mitotic activity in chick wing and leg buds from embryonic day 4 to embryonic day 9. During early stages, butyrylcholinesterase is elevated in cells under the apical ectodermal ridge and around invading motoraxons, while acetylcholinesterase is found in the chondrogenic core, on motoraxons and along the ectoderm. Peanut agglutinin binds to the apical ectodermal ridge and most prominently to the chondrogenic core. Measurements of thymidine incorporation and enzyme activities were consistent with our histological findings. Butyrylcholinesterase is concentrated near proliferative zones and periods, while acetylcholinesterase is associated with low proliferative activity. At late stages of limb development, acetylcholinesterase is concentrated in muscles and nonexistent within bones, while butyrylcholinesterase shows an inverse pattern. Thus, as in other systems, in limb formation butyrylcholinesterase is a transmitotic marker preceding differentiation, acetylcholinesterase is found on navigating axons, while peanut agglutinin appears in non-invaded regions. These data suggest roles for cholinesterases as positive regulators and peanut-agglutinin-binding proteins as negative regulators of neural differentiation.

The carbohydrate epitope HNK-1 is present on all inactive, but not on all active forms of chicken butyrylcholinesterase.

The HNK-1 epitope as a hallmark of many cell adhesion molecules is supposed to convey positive cellular interactions. Here, we report that in the adult chick the HNK-1 epitope is absent from active serum butyrylcholinesterases (BChE), but is strongly expressed on all inactive serum BChEs and on active brain BChE. These data further support roles of cholinesterases in cell adhesion, particularly so for their inactive forms. Moreover, we show that the HNK-1-positive BChEs belong to different types of glycoproteins.

Novel inactive and distinctively glycosylated forms of butyrylcholinesterase from chicken serum.

Three different homologues of butyrylcholinesterase (BChE) with 75-, 62-, and 54-kDa subunit size are isolated from adult chicken serum, and all show very low or zero enzyme activity. Although the active BChE from serum with a subunit size of 81 kDa forms tetramers, the 75-kDa protein is isolated as a dimer. The homology of the 75-kDa protein with active BChE is shown by immunoreactivity with BChE-specific monoclonal antibodies, by coisolation with the active BChE, and by their identical first six N-terminal amino acids. By deglycosylation of these proteins and by their differential lectin binding, we show that the active BChE is an N-glycosylated protein of the triantennary type, whereas the inactive 75-kDa protein is O-glycosylated. These data show for the first time the existence of (1) multiple inactive forms of BChE, (2) secreted inactive cholinesterases, because they are found in serum, and (3) an O-glycosylated cholinesterase. Because cholinesterases can regulate neurite growth in vitro by a nonenzymatic mechanism, these data strongly support that both inactive and active forms of BChE may be involved in noncholinergic communication, possibly depending on particular glycosylation patterns.

Use of ELISA to G4 antigen to quantitate neurite outgrowth in the chick both in vivo and in vitro.

The G4 glycoprotein is found on the earliest developing neurite tracts of the chick embryo. An ELISA is introduced here to quantify the amount of G4-expressing neurites in the picogram range. In this double-sandwich assay, an anti-G4 monoclonal antibody fixes the G4 antigen to the plastic surface, which then is detected by a polyclonal antiserum; nonspecific background is decreased by competitive displacement. The sensitivity of the assay allows us to follow quantitatively the very first neurite growth in embryonic heads, trunks, retinae, and brains. G4-based neurite growth is shown to occur earlier in heads than in trunks; in brain it is nearly 10-fold higher than in the retina by embryonic day 8. By determination of acetylcholinesterase (AChE) activities from the same homogenates, our earlier histochemical findings are verified now on a quantitative basis, again showing that AChE consistently precedes G4 antigen. Moreover, as an in vitro example, the G4 ELISA is applied to the nerve growth factor (NGF) standard bioassay on dorsal root ganglia; the half-maximal response is reached at approximately 10 ng/ml of NGF for G4-based neurite growth and at approximately 1 ng/ml of NGF for AChE expression, respectively.

Cholinesterases regulate neurite growth of chick nerve cells in vitro by means of a non-enzymatic mechanism.

Cholinesterases present homologies with some cell adhesion molecules; however, it is unclear whether and how they perform adhesive functions. Here, we provide the first direct evidence showing that neurite growth in vitro from various neuronal tissues of the chick embryo can be modified by some, but not all, anticholinesterase agents. By quantifying the neuritic G4 antigen in tectal cell cultures, the effect of anticholinesterases on neurite growth is directly compared with their cholinesterase inhibitory action. BW 284C51 and ethopropazine, inhibiting acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), respectively, strongly decrease neurite growth in a dose-dependent manner. However, echothiophate which inhibits both cholinesterases, does not change neuritic growth. These quantitative data are supplemented by morphological observations in retinal explant cultures grown on striped laminin carpets, viz., defasciculation of neurite bundles by BW 284C51 and Bambuterol occurs, indicating that these drugs disturb adhesive mechanisms. These data strongly suggest that a) cholinesterases can participate in regulating axonal growth, b) both AChE and BChE can perform such a nonsynaptic function, and c) this function is not the result of the enzyme activity per se, since at least one drug was found that inhibits all cholinesterase activities but not neurite growth. Thus, a secondary site on cholinesterase molecules must be responsible for adhesive functions.

Chicken retinospheroids as developmental and pharmacological in vitro models: acetylcholinesterase is regulated by its own and by butyrylcholinesterase activity.

The phylo- and ontogenetically related enzymes butyrylcholinesterase (BChE) and acetylcholinesterase (AChE) are expressed consecutively at the onset of avian neuronal differentiation. In order to investigate their possible co-regulation, we have studied the effect of highly selective inhibitors on each of the cholinesterases with respect to their expression in rotary cultures of the retina (retinospheroids) and stationary cultures of the embryonic chick tectum. Adding the irreversible BChE inhibitor iso-OMPA to reaggregating retinal cells has only slight morphological effects and fully inhibits BChE expression. Unexpectedly, iso-OMPA also suppresses the expression of AChE to 35%-60% of its control activity. Histochemically, this inhibition is most pronounced in fibrous regions. The release of AChE into the media of both types of cultures is inhibited by iso-OMPA by more than 85%. Control experiments show that AChE suppression by the BChE inhibitor is only partially explainable by direct cross-inhibition of iso-OMPA on AChE. In contrast, the treatment of retinospheroids with the reversible AChE inhibitor BW284C51 first accelerates the expression of AChE and then leads to a rapid decay of the spheroids. After injection of BW284C51 into living embryos, we find that AChE is expressed prematurely in cells that normally express BChE. We conclude that the cellular expression of AChE is regulated by the amount of both active BChE and active AChE within neuronal tissues. Thus, direct interaction with classical cholinergic systems is indicated for the seemingly redundant BChE.

Developmental maps of acetylcholinesterase and G4-antigen of the early chicken brain: long-distance tracts originate from AChE-producing cell bodies.

After approaching the outer surface of the neuroepithelium, postmitotic cell bodies abruptly start to synthesize acetylcholinesterase (AChE). Their easy histochemical detection allows us to trace sensitively spatiotemporal patterns of differentiation processes of the chicken nervous system. To investigate the relationship between postmitotic AChE production and the first formation of neurites, AChE histochemistry is combined here with immunohistochemistry using the neurite-specific G4-antibody. Spatial computer reconstructions from double-stained serial sections of whole brains of H.H. stages 10-20 demonstrate that G4-neurite expression spatio-temporally follows the expression of AChE in its complex polycentric pattern closely, the details of which have been described earlier. By comparing both differentiative steps at the single cell level reveals that a great majority (if not all) of the G4-positive neurites originate from AChE-positive cell bodies. Based on both the computer reconstructions as well as single cell analysis, including [3H]-thymidine pulse-experiments followed by autoradiography, we conclude, that AChE expression precedes formation of G4-neurites by about 15 h. In addition, the reconstructions provide the first detailed maps of G4-fiber tract formation and shows that G4-neurites form fascicles, most of which travel over long distances to targets within or without the central nervous system (CNS). This is the first demonstration for the entire young chicken brain which verifies that AChE-expressing cells, generally, are those that will establish efferents to distant targets.