Changes in postural sway and its fractions in conditions of postural instability

We investigated changes in postural sway and its fractions associated with manipulations of the dimensions of the support area. Nine healthy adults stood as quietly as possible, with their eyes open, on a force plate as well as on 5 boards with reduced support area. The center of pressure (COP) trajectory was computed and decomposed into rambling (Rm) and trembling (Tr) trajectories. Sway components were quantified using RMS (root mean square) value, average velocity, and sway area. During standing on the force plate, the RMS was larger for the anterior-posterior (AP) sway components than for the mediolateral (ML) components. During standing on boards with reduced support area, sway increased in both directions. The increase was more pronounced when standing on boards with a smaller support area. Changes in the larger dimension of the support area also affected sway, but not as much as changes in the smaller dimension. ML instability had larger effects on indices of sway compared to AP instability. The average velocity of Rm was larger while the average velocity of Tr was smaller in the AP direction vs. the ML direction. The findings can be interpreted within the hypothesis of an active search function of postural sway. During standing on boards with reduced support area, increased sway may by itself lead to loss of balance. The findings also corroborate the hypothesis of Duarte and Zatsiorsky that Rm and Tr reveal different postural control mechanisms.     

Reproducible volar partial lacerations in flexor tendons: a new device for biomechanical studies

A device was designed to create clinically relevant, precise partial flexor digitorum profundus tendon lacerations for in vitro studies but can be adapted for in vivo studies. This caliper-based system utilizes a direct measurement of the tendon height and assumes an elliptical cross section to select the depth of the cut. The accuracy was tested on 60 cuts on 12 human tendons lacerated to an expected 50% or 75% of their cross-sectional area, based on the assumption that the cross-section was elliptical in shape. The cuts were made in portions of the tendon that varied in cross-sectional shape and size. The cut surface of the laceration was colored with Methylene blue and then the laceration was completed. The tendon cross-section was digitally imaged and the respective areas of the stained and unstained regions were evaluated using image-processing software. The mean lacerated areas were 52% (SD 5%) and 73% (SD 6%) for targeted lacerations of 50% and 75%, respectively. The device thus appears to be accurate within an acceptable 5% margin of error from the expected area, and adaptable to intra- and inter-tendinous size variations.     

Contraction of collagen gels seeded with tendon cells

Knowledge of the adaptation of the soft tissue to mechanical factors and biomolecules would be essential to better understand the mechanism of tendon injury and to improve the outcome of tendon repair. The responses to these factors could be different for the distinct types of cells in the tendon: cells from the tendon sheath, fibroblasts from the epitenon surface, or fibroblasts from the internal endotenon. In this study, we examined the mechanical and histological characteristics of the rate of contraction of the collagen gel seeded with epitenon and endotenon fibroblasts. The rate of contraction and the mechanical property of the contracted construct depend on the gel concentration and also the treatment of TGF-beta1.     

No evidence for learned mating discrimination in male Drosophila pseudoobscura

Background  

Since females often pay a higher cost for heterospecific matings, mate discrimination and species recognition are driven primarily by female choice. In contrast, frequent indiscriminate matings are hypothesized to maximize male fitness. However, recent studies show that previously indiscriminate males (e.g., Drosophila melanogaster and Poecilia reticulata) can learn to avoid heterospecific courtship. This ability of males to discriminate against heterospecific courtship may be advantageous in populations where two species co-occur if courtship or mating is costly.     

Reflex sympathetic dystrophy syndrome: consensus report of an ad hoc committee of the American Association for Hand Surgery on the definition of reflex sympathetic dystrophy syndrome

This report proposes that reflex sympathetic dystrophy be defined as a pain syndrome in which the pain is accompanied by loss of function and evidence of autonomic dysfunction. In the clinical setting, this diagnosis is usually associated with other anatomic and psychological diagnoses and may be associated with a variety of systemic illnesses and medicolegal factors. All components should be assessed before a treatment plan is established. Priorities should go to emergency care, acute injuries, and systemic illness, psychiatric problems, and chronic anatomic problems, in that order. Early, accurate diagnosis improves prognosis.     

BOLA‐DRB3 gene polymorphisms influence bovine leukaemia virus infection levels in Holstein and Holstein × Jersey crossbreed dairy cattle

Bovine leukemia virus (BLV) infections, causing persistent lymphocytosis and lethal lymphosarcoma in cattle, have reached high endemicity on dairy farms. We observed extensive inter‐individual variation in the level of infection (LI) by assessing differences in proviral load in peripheral blood. This phenotypic variation appears to be determined by host genetics variants, especially those located in the BoLA‐DRB3 MHCII molecule. We performed an association study using sequencing‐based typed BOLA‐DRB3 alleles from over 800 Holstein and Holstein × Jersey cows considering LI in vivo and accounting for filial relationships. The DBR3*0902 allele was associated with a low level of infection (LLI) (<1% of circulating infected B‐cells), whereas the DRB3*1001 and DRB3*1201 alleles were related to a high level of infection (HLI). We found evidence that 13 polymorphic positions located in the pockets of the peptide‐binding cleft of the BOLA‐DRB3 alleles were associated with LI. DRB3*0902 had unique haplotypes for each of the pockets: Ser¹³‐Glu⁷⁰‐Arg⁷¹‐Glu⁷⁴ (pocket 4), Ser¹¹‐Ser³⁰ (pocket 6), Glu²⁸‐Trp⁶¹‐Arg⁷¹ (pocket 7) and Asn³⁷‐Asp⁵⁷ (pocket 9), and all of them were significantly associated with LLI. Conversely, Lys¹³‐Arg⁷⁰‐Ala⁷¹‐Ala⁷⁴ and Ser¹³‐Arg⁷⁰‐Ala⁷¹‐Ala⁷⁴, corresponding to the DRB3*1001 and *1201 alleles respectively, were associated with HLI. We showed that the specific amino acid pattern in the DRB3*0902 peptide‐binding cleft may be related to the set point of a very low proviral load level in adult cows. Moreover, we identified two BOLA‐DRB3 alleles associated with a HLI, which is compatible with a highly contagious profile.     

Functional and structural insight into properdin control of complement alternative pathway amplification

Properdin (FP) is an essential positive regulator of the complement alternative pathway (AP) providing stabilization of the C3 and C5 convertases, but its oligomeric nature challenges structural analysis. We describe here a novel FP deficiency (E244K) caused by a single point mutation which results in a very low level of AP activity. Recombinant FP E244K is monomeric, fails to support bacteriolysis, and binds weakly to C3 products. We compare this to a monomeric unit excised from oligomeric FP, which is also dysfunctional in bacteriolysis but binds the AP proconvertase, C3 convertase, C3 products and partially stabilizes the convertase. The crystal structure of such a FP-convertase complex suggests that the major contact between FP and the AP convertase is mediated by a single FP thrombospondin repeat and a small region in C3b. Small angle X-ray scattering indicates that FP E244K is trapped in a compact conformation preventing its oligomerization. Our studies demonstrate an essential role of FP oligomerization in vivo while our monomers enable detailed structural insight paving the way for novel modulators of complement.