Modular Design of a Passive, Low-Cost Prosthetic Knee Mechanism to Enable Able-Bodied Kinematics for Users With Transfemoral Amputation

There is a significant need for low-cost, high-performance prosthetic knee technology for transfemoral amputees in India. Replicating able-bodied gait in amputees is biomechanically necessary to reduce the metabolic cost, and it is equally important to mitigate the socio-economic discrimination faced by amputees in developing countries due to their conspicuous gait deviations. This paper improves upon a previous study of a fully passive knee mechanism, addressing the issues identified in its user testing in India. This paper presents the design, analysis and bench-level testing of the three major functional modules of the new prosthetic knee architecture: (i) a four-bar latch mechanism for achieving stability during stance phase of walking, (ii) an early stance flexion module designed by implementing a fully adjustable mechanism, and (iii) a hydraulic rotary damping system for achieving smooth and reliable swing-phase control

Medical ultrasound system with integrated force measurement

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.Cataloged from PDF version of thesis.Includes bibliographical references (pages 107-110).Ultrasound is a commonly used medical imaging modality for non-invasive examination of soft tissue. Clinical ultrasound scanning requires significant contact of the transducer face with the patient, and the contact force exerted by the sonographer can vary widely throughout a scan or from scan to scan. This thesis explores the design and development of an electromechanical system to measure the contact force during ultrasound scanning. The device is a handheld ultrasound probe with force sensors integrated into its housing such that the force distribution across the ultrasound transducer face can be measured. The device was used to perform shear wave elastography on tissue-mimicking phantoms and ex vivo tissue at varying force distributions. A gradient in applied pressure introduced a gradient in elasticity across the image for ex vivo tissue but not for phantoms. To consider how the device integrates into the overall system, a human factors study was done to compare feedback modalities provided to the human operator during ultrasound scanning. Visual feedback was more effective than haptic feedback for force tracking, but at expense of ultrasound path tracking. Lastly, two methods of data synchronization of the acquired force data and ultrasound images are considered. A three tap software synchronization method is a feasible alternative when hardware synchronization is unavailable. As a whole, this system will improve the repeatability and capabilities of ultrasound imaging.by Athena Yeh Huang.S.M

BLMP-1/Blimp-1 Regulates the Spatiotemporal Cell Migration Pattern in <i>C. elegans</i>

<div><p>Spatiotemporal regulation of cell migration is crucial for animal development and organogenesis. Compared to spatial signals, little is known about temporal signals and the mechanisms integrating the two. In the <i>Caenorhabditis elegans</i> hermaphrodite, the stereotyped migration pattern of two somatic <u>d</u>istal <u>t</u>ip <u>c</u>ells (DTCs) is responsible for shaping the gonad. Guidance receptor UNC-5 is necessary for the dorsalward migration of DTCs. We found that BLMP-1, similar to the mammalian zinc finger transcription repressor Blimp-1/PRDI-BF1, prevents precocious dorsalward turning by inhibiting precocious <i>unc-5</i> transcription and is only expressed in DTCs before they make the dorsalward turn. Constitutive expression of <i>blmp-1</i> when BLMP-1 would normally disappear delays <i>unc-5</i> transcription and causes turn retardation, demonstrating the functional significance of <i>blmp-1</i> down-regulation. Correct timing of BLMP-1 down-regulation is redundantly regulated by heterochronic genes <i>daf-12</i>, <i>lin-29</i>, and <i>dre-1</i>, which regulate the temporal fates of various tissues. DAF-12, a steroid hormone receptor, and LIN-29, a zinc finger transcription factor, repress <i>blmp-1</i> transcription, while DRE-1, the F-Box protein of an SCF ubiquitin ligase complex, binds to BLMP-1 and promotes its degradation. We have therefore identified a gene circuit that integrates the temporal and spatial signals and coordinates with overall development of the organism to direct cell migration during organogenesis. The tumor suppressor gene product FBXO11 (human DRE-1 ortholog) also binds to PRDI-BF1 in human cell cultures. Our data suggest evolutionary conservation of these interactions and underscore the importance of DRE-1/FBXO11-mediated BLMP-1/PRDI-BF1 degradation in cellular state transitions during metazoan development.</p></div

DTC migration defects of <i>blmp-1</i> mutants.

<p>(A) Schematic diagram showing the path and direction of DTC migration in phases I, II, and III. The developmental stage in which each migration phase occurs is indicated on the right. The solid line and arrow show, respectively, the path and direction of each migration phase. (B–F) DIC images of adult wild-type (B) and <i>blmp-1(s71)</i> (C–F) gonads. The black line shows the migratory path, starting from the asterisk, the DTC is indicated by the black arrowhead, and the white arrowhead indicates the position at which the DTC initiated dorsal phase II migration. In (C–F), the DTC had a shorter phase I migratory path (distance between the asterisk and white arrowhead) than the wild-type DTC (B); in addition, the DTC in (C) had a longer phase III migration path, that in (D) had a slanted phase II migration path (see text for details), and that in (E) moved in the opposite direction during phase III migration. (F) The DTC had a similar migratory trajectory to that shown in (E), except that it failed to stay on the dorsal side during phase III migration. The gonadal arm shown in B–E is posterior, while that in F is anterior, as the defect was only observed in this arm, as shown in <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1004428#pgen.1004428.s006" target="_blank">Table S1</a>. The picture in F was flipped 180 degrees so that its migration trajectory could be easily compared to those in B–E. Scale bar 40 µm. (G) Percentage of the indicated <i>blmp-1</i> mutants and transgenic worms with a DTC migration defect (shown in <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1004428#pgen-1004428-g001" target="_blank">Figure 1C–F</a>). A: anterior DTC, P: posterior DTC. At least 50 worms were scored for each genotype.</p

Genetic interactions between <i>blmp-1</i> and the heterochronic genes <i>lin-29</i>, <i>dre-1</i>, and <i>daf-12</i> in the timing of the DTC dorsal turn.

a<p>Percentage of animals in which the posterior DTCs showed a wild-type, premature, or retarded dorsal turn. At least 50 worms were scored for each genotype. Only the data for the posterior DTCs are shown.</p>b<p>Posterior DTCs with a path-finding defect were seen in 3% of <i>lin-29(n546); daf-12(rh61rh411)</i> worms and 2% of dre-1(dh99);daf-12(rh61rh411) worms.</p>c<p>Posterior DTCs with no obvious dorsal phase II migration and with the reversal of migration direction in centripetal phase III movement were seen in 16% of <i>blmp-1 (s71); lin-29(RNAi)</i> and 26% of <i>blmp-1(s71)</i>; <i>daf-12(rh61rh41)</i> worms. This defect may be caused by abnormal pathfinding or retardation in phase II and III migration.</p

BLMP-1 expression pattern and its regulation.

<p>(A) Representative images of a wild-type embryo (a) or larva (b–d) stained with anti-BLMP-1 antibodies. (a) In the 1.5-fold embryo, BLMP-1 is detected in Hyp7, V cells, and P cell precursors. (b–d) In the larva, BLMP-1 is detected in hypodermal and seam cells (b and c), vulval cells (c), and posterior intestinal cells (d). Scale bar 40 µm. (B) BLMP-1 levels in wild-type DTCs at different larval stages revealed by immunostaining with anti-BLMP-1 antibody (a–c) or together with DAPI staining (d–f). (a) BLMP-1 is detected during centrifugal phase I migration in L2. (b, c) No BLMP-1 is detected during dorsal phase II migration in late L3 (b) or during centripetal phase III migration in L4 (c). (d, e, f) The same worms as those in, respectively, a, b, or c stained with DAPI to label nuclei and to examine the developmental stage of the gonad. Scale bar 20 µm. The arrowheads indicate DTCs. (C) The DIC (a, b) and immunostaining (c, d) images of <i>blmp-1(s71)</i> (a, c) and <i>blmp-1(tm548)</i> (b,d) embryos stained by anti-BLMP-1 antibodies. Scale bar 10 µm. (D) Presence of BLMP-1 at the L4 stage in the DTCs of the double mutants <i>lin-29;dre-1</i> (a) and <i>dre-1;daf-12</i> (b), as revealed by immunostaining with anti-BLMP-1 antibodies. (c, d) The same worms as those in a and b, respectively, stained with DAPI. Scale bar 20 µm.</p

Spatiotemporal regulation of DTC migration.

<p><i>blmp-1</i> and lin-42 negatively regulate the timing of the DTC dorsal turn, whereas <i>daf-12</i>, <i>dre-1</i>, and <i>lin-29</i> function in a redundant fashion to positively regulate the turn. Although <i>daf-12</i> is activated by DAs (dafachronic acids) and <i>lin-42</i> inhibits <i>daf-12</i> and <i>lin-29</i>, they are boxed together for convenience. A double-negative feedback loop between <i>blmp-1</i> and <i>lin-29</i> may contribute to the switch-like turning process of DTCs (see text for detail). Gene interactions that occur in phase I migration are shown in green and those that occur in phase II migration are shown in red.</p

BLMP-1 and DRE-1 are co-immunoprecipitated in human cell cultures, as are their human orthologs PRDI-BF1 and FBXO11.

<p>HEK293T cells were transfected with the indicated plasmids. Expression of the indicated plasmids in the whole cell lysate (WCL) is shown in the bottom panels, with tubulin or GAPDH as the loading control. (A, B) Co-immunoprecipitation of <i>C. elegans</i> Myc-DRE-1 and HA-BLMP-1. (A) Myc-DRE-1 was immunoprecipitated with anti-Myc antibodies and Western blots were probed with anti-HA antibodies to detect HA-BLMP-1 and with anti-Myc antibodies to detect Myc-DRE-1. (B) HA-BLMP-1 was immunoprecipitated with anti-HA antibodies and Western blots were probed with anti-Myc antibodies to detect Myc-DRE-1 and with anti-HA antibodies to detect HA-BLMP-1. (C) Co-immunoprecipitation of <i>C. elegans</i> Myc-DRE-1 and HA-BLMP-1. HA-PRDI-BF1 was immunoprecipitated with anti-HA antibodies and Western blots were probed with anti-Myc antibodies to detect Myc-FBXO11 and with anti-cullin 1 antibodies to detect cullin 1.</p

Gene structure of <i>blmp-1</i>.

<p>Gene structure of <i>blmp-1</i> deduced from genomic and cDNA sequences. The boxes indicate exons. The regions encoding the PRDI-BF1-RIZ1 homologous region (PR) domain, nuclear localization signal (NLS), and zinc finger motifs are marked, as is the <i>trans</i> spliced leader SL1. The positions of the <i>blmp-1</i> mutant alleles, including the region corresponding to the <i>tm548</i> deletion, are indicated.</p

DTCs in the <i>blmp-1</i> mutant undergo a precocious dorsal turn.

<p>(A) DIC images of wild-type (WT) and <i>blmp-1(s71)</i> posterior gonadal arms during the early L3 (top panels) and late L3 (bottom panels) stages. (a–d) In early L3, when the worms were in the one-P6.p-cell stage (b, d), the wild-type DTC (a) was still in phase I migration, while the <i>blmp-1</i> DTC (c) had already made a dorsal turn. (e–h) In late L3, when the worms were in the four-P6.p-cell stage (f, h), the wild-type DTC (e) had just begun the dorsal turn, while the <i>blmp-1</i> DTC (g) had already completed the dorsal phase II migration and undergone centripetal phase III migration. In the left panel, the arrow and dotted line indicate, respectively, the DTC and its migratory path. In the right panel, the arrowhead indicates the P6.p division stage of the same worm shown in the left panel. (B) The percentage of worms with anterior (left) and posterior (right) DTCs that initiated the phase II dorsal turn at the indicated division stage of the P6.p cell (shown in the center) in wild-type (black bars) and <i>blmp-1(s71)</i> (gray bars) worms. At least 33 worms were examined for each genotype.</p