Changes in Muscles and Tendons Due to Neural Motor Disorders: Implications for Therapeutic Intervention

Patients with an upper motor neurone syndrome (CP) suffer from many disabling primary symptoms: spasms, weakness, and loss of dexterity. These primary ‘neurogenic’ symptoms often lead to secondary disabilities, muscle contractures, and tertiary effects, bone deformations. A common symptom of CP is hypertonia, with. the consequence that the involved muscles remain in an excessively shortened length for most of the time. As a normal reaction of the muscle tissue, the number of sarcomeres is reduced and the muscle fibers shorten permanently: a contracture develops. A possible second type of contracture is that normal muscle lengthening along with bone growth is affected. Current treatments for the secondary effects include (1) reduction of muscle force, (2)lengthening of the muscle fibers by serial plaster casts, and (3)surgical lengthening of tendons or aponeurosis. The choice of treatment depends on the cause of the functional deficit. Bone tissue also adapts itself to abnormal forces, especially in the growth period. The hypertonias or contractures of CP so may give rise to bone malformations that interfere with function (e.g. femur endorotation) or may reduce the action of muscles by changing the lever arm (e.g. ankle varus). Although prevention should always be preferred, a timely surgical intervention cannot always be avoided. The differences in treatment for the various groups require and justify an extensive laboratory investigation, including EMG recordings in gait, measurement of passive elastic properties, and long-term observation of the hypertonia

Rapid and MR-Independent IK1 activation by aldosterone during ischemia-reperfusion

In ST elevation myocardial infarction (STEMI) context, clinical studies have shown the deleterious effect of high aldosterone levels on ventricular arrhythmia occurrence and cardiac mortality. Previous in vitro reports showed that during ischemia-reperfusion, aldosterone modulates K+ currents involved in the holding of the resting membrane potential (RMP). The aim of this study was to assess the electrophysiological impact of aldosterone on IK1 current during myocardial ischemia-reperfusion. We used an in vitro model of “border zone” using right rabbit ventricle and standard microelectrode technique followed by cell-attached recordings from freshly isolated rabbit ventricular cardiomyocytes. In microelectrode experiments, aldosterone (10 and 100 nmol/L, n=7 respectively) increased the action potential duration (APD) dispersion at 90% between ischemic and normoxic zones (from 95±4ms to 116±6 ms and 127±5 ms respectively, P<0.05) and reperfusion-induced sustained premature ventricular contractions occurrence (from 2/12 to 5/7 preparations, P<0.05). Conversely, potassium canrenoate 100 nmol/L and RU 28318 1 μmol/l alone did not affect AP parameters and premature ventricular contractions occurrence (except Vmax which was decreased by potassium canrenoate during simulated-ischemia). Furthermore, aldosterone induced a RMP hyperpolarization, evoking an implication of a K+ current involved in the holding of the RMP. Cell-attached recordings showed that aldosterone 10 nmol/L quickly activated (within 6.2±0.4 min) a 30 pS K+-selective current, inward rectifier, with pharmacological and biophysical properties consistent with the IK1 current (NPo =1.9±0.4 in control vs NPo=3.0±0.4, n=10, P<0.05). These deleterious effects persisted in presence of RU 28318, a specific MR antagonist, and were successfully prevented by potassium canrenoate, a non specific MR antagonist, in both microelectrode and patch-clamp recordings, thus indicating a MR-independent IK1 activation. In this ischemia-reperfusion context, aldosterone induced rapid and MR-independent deleterious effects including an arrhythmia substrate (increased APD90 dispersion) and triggered activities (increased premature ventricular contractions occurrence on reperfusion) possibly related to direct IK1 activation

Open source software for semi-automated histomorphometry of bone resorption and formation parameters

Micro-CT analysis has become the standard method for assessing bone volume and architecture in small animals. However, micro-CT does not allow the assessment of bone turnover parameters such as bone formation rate and osteoclast (OC) number and surface. For these crucial variables histomorphometric analysis is still an essential technique. Histomorphometry however, is time consuming and, especially in mouse bones, OCs can be difficult to detect. The main purpose of this study was to develop and validate a relatively easy and rapid method to measure static and dynamic bone histomorphometry parameters. Here we present the adaptation of established staining protocols and three novel open source image analysis packages: TrapHisto, OsteoidHisto and CalceinHisto that allow rapid, semi-automated analysis of histomorphometric bone resorption, osteoid, and calcein double labelling parameters respectively. These three programs are based on ImageJ, but use a relatively simple user interface that hides the underlying complexity of the image analysis

Tilings, tiling spaces and topology

To understand an aperiodic tiling (or a quasicrystal modeled on an aperiodic tiling), we construct a space of similar tilings, on which the group of translations acts naturally. This space is then an (abstract) dynamical system. Dynamical properties of the space (such as mixing, or the spectrum of the translation operator) are closely related to bulk properties of the individual tilings (such as the diffraction pattern). The topology of the space of tilings, particularly the Cech cohomology, gives information on how the original tiling can be deformed. Tiling spaces can be constructed as inverse limits of branched manifolds.Comment: 8 pages, including 2 figures, talk given at ICQ

Diffractive point sets with entropy

After a brief historical survey, the paper introduces the notion of entropic model sets (cut and project sets), and, more generally, the notion of diffractive point sets with entropy. Such sets may be thought of as generalizations of lattice gases. We show that taking the site occupation of a model set stochastically results, with probabilistic certainty, in well-defined diffractive properties augmented by a constant diffuse background. We discuss both the case of independent, but identically distributed (i.i.d.) random variables and that of independent, but different (i.e., site dependent) random variables. Several examples are shown.Comment: 25 pages; dedicated to Hans-Ude Nissen on the occasion of his 65th birthday; final version, some minor addition

Palindromic complexity of trees

We consider finite trees with edges labeled by letters on a finite alphabet $\varSigma$. Each pair of nodes defines a unique labeled path whose trace is a word of the free monoid $\varSigma^*$. The set of all such words defines the language of the tree. In this paper, we investigate the palindromic complexity of trees and provide hints for an upper bound on the number of distinct palindromes in the language of a tree.Comment: Submitted to the conference DLT201

Random fields on model sets with localized dependency and their diffraction

For a random field on a general discrete set, we introduce a condition that the range of the correlation from each site is within a predefined compact set D. For such a random field omega defined on the model set Lambda that satisfies a natural geometric condition, we develop a method to calculate the diffraction measure of the random field. The method partitions the random field into a finite number of random fields, each being independent and admitting the law of large numbers. The diffraction measure of omega consists almost surely of a pure-point component and an absolutely continuous component. The former is the diffraction measure of the expectation E[omega], while the inverse Fourier transform of the absolutely continuous component of omega turns out to be a weighted Dirac comb which satisfies a simple formula. Moreover, the pure-point component will be understood quantitatively in a simple exact formula if the weights are continuous over the internal space of Lambda Then we provide a sufficient condition that the diffraction measure of a random field on a model set is still pure-point.Comment: 21 page

Repetitions in beta-integers

Classical crystals are solid materials containing arbitrarily long periodic repetitions of a single motif. In this paper, we study the maximal possible repetition of the same motif occurring in beta-integers -- one dimensional models of quasicrystals. We are interested in beta-integers realizing only a finite number of distinct distances between neighboring elements. In such a case, the problem may be reformulated in terms of combinatorics on words as a study of the index of infinite words coding beta-integers. We will solve a particular case for beta being a quadratic non-simple Parry number.Comment: 11 page

Recurrence in 2D Inviscid Channel Flow

I will prove a recurrence theorem which says that any $H^s$ ($s>2$) solution to the 2D inviscid channel flow returns repeatedly to an arbitrarily small $H^0$ neighborhood. Periodic boundary condition is imposed along the stream-wise direction. The result is an extension of an early result of the author [Li, 09] on 2D Euler equation under periodic boundary conditions along both directions

Use of 3D printed connectors to redesign full face snorkeling masks in the COVID-19 era: a preliminary technical case-study

The COVID-19 pandemic resulted in severe shortages of personal protection equipment and non-invasive ventilation devices. As traditional supply chains could not meet up with the demand, makeshift solutions were developed and locally manufactured by rapid prototyping networks. Among the different global initiatives, retrofitting of full-face snorkeling masks for Non-Invasive-Ventilation (NIV) applications seems the most challenging. This article provides a systematic overview of rapid prototyped - 3D printed - designs that enable attachment of medical equipment to snorkeling masks, highlighting potential and challenges in additive manufacturing. The different NIV connector designs are compared on low-cost 3D fabrication time and costs, which allows a rapid assessment of developed connectors for health care workers in urgent need of retrofitting snorkeling masks for NIV purposes. Challenges and safety issues of the rapid prototyping approach for healthcare applications during the pandemic are discussed as well. When critical parameters such as the final product cost, geographical availability of the feedstock and the 3D printers and the medical efficiency of the rapid prototyped products are well considered before deploying decentralized 3D printing as manufacturing method, this rapid prototyping strategy contributed to reduce personal protective equipment and NIV shortages during the first wave of the COVID-19 pandemic. It is also concluded that it is crucial to carefully optimize material and printer parameter settings to realize best fitting and airtight connector-mask connections, which is heavily depending on the chosen feedstock and type of printer