Optimality in forward dynamics simulations

This paper discusses a methodology and an algorithm for the analysis of dynamics of bio-mechanical systems, and in particular of optimal movement patterns between initial and target configurations. The basic formulation utilizes a finite element time discretization and establishes a large set of equations in displacements and forces. These are solved simultaneously for the whole time interval considered. The algorithm allows different optimization criteria for the movement, based on either the smoothness of the movement or the minimization of needed controls or control rates. It is primarily aimed at musculoskeletal simulations with either the joint resultant moments or the redundant muscular tensions as unknowns. Kinetic and kinematic constraints can be introduced for the obtained movement. Examples show that the obtained results are strongly dependent on the optimality criterion used. Systematic usage of the algorithm can improve knowledge about optimal motion planning.     

Sex- and depot-specific lipolysis regulation in human adipocytes: interplay between adrenergic stimulation and glucocorticoids

The purpose of this investigation was to explore interactions between adrenergic stimulation, glucocorticoids, and insulin on the lipolytic rate in isolated human adipocytes from subcutaneous and omental fat depots, and to address possible sex differences. Fat biopsies were obtained from 48 nondiabetic subjects undergoing elective abdominal surgery. Lipolysis rate was measured as glycerol release from isolated cells and proteins involved in lipolysis regulation were assessed by immunoblots. Fasting blood samples were obtained and metabolic and inflammatory variables were analyzed. In women, the rate of 8-bromo-cAMP- and isoprenaline-stimulated lipolysis was approximately 2- and 1.5-fold higher, respectively, in subcutaneous compared to omental adipocytes, whereas there was no difference between the two depots in men. Dexamethasone treatment increased the ability of 8-bromo-cAMP to stimulate lipolysis in the subcutaneous depot in women, but had no consistent effects in fat cells from men. Protein kinase A, Perilipin A, and hormone sensitive lipase content in adipocytes was not affected by adipose depot, sex, or glucocorticoid treatment. In conclusion, catecholamine and glucocorticoid regulation of lipolysis in isolated human adipocytes differs between adipose tissue depots and also between sexes. These findings may be of relevance for the interaction between endogenous stress hormones and adipose tissue function in visceral adiposity and the metabolic syndrome.     

Attractiveness of women's body odors over the menstrual cycle: the role of oral contraceptives and receiver sex

It is a long held assumption that women have concealed ovulation,which means that men do not know when women's menstrual cyclesare in their most fertile phase. Recent empirical results haveprovided evidence that ovulation may not be totally concealedfrom pair-bonded males, but the generality and the mechanismsof the finding demand further study. To examine the possibleadaptive value of the phenomenon, it is necessary to study whetherthe ability to detect ovulation is confined to males. We studiedthese questions in an experiment in which male and female ratersrated the sexual attractiveness and intensity of T-shirts' odorsworn by 42 women using oral contraceptives (pill users) andby 39 women without oral contraceptives (nonusers). Males ratedthe sexual attractiveness of nonusers highest at midcycle. However,female raters showed only a nonsignificant trend for this relationship.Neither sex rated attractiveness of the odors of pill usersaccording to their menstrual cycle. The results indicate thatmen can use olfactory cues to distinguish between ovulatingand nonovulating women. Furthermore, the contrasting resultsbetween pill users and nonusers may indicate that oral contraceptivesdemolish the cyclic attractiveness of odors. Together, thesefindings give more basis for the study of the role of odorsin human sexual behavior.     

Test-retest reliability of EMG and peak torque during repetitive maximum concentric knee extensions.

The aim of this study was to investigate the reliability of peak torque and surface electromyography (EMG) variable's root mean square (RMS) and mean frequency (MNF) during an endurance test consisting of repetitive maximum concentric knee extensions. Muscle fatigue has been quantified in several ways, and in isokinetic testing it is based on a set of repetitive contractions. To assess test-retest reliability, two sets of 100 dynamic maximum concentric knee extensions were performed using an isokinetic dynamometer. The two series were separated by 7-8 days. The subjects relaxed during the passive flexion phase. Twenty (10 men and 10 women) clinically healthy subjects volunteered.Peak torque and EMG from rectus femoris, vastus medialis, vastus lateralis and biceps femoris were recorded. RMS and MNF were calculated from the EMG signal. The reliability was calculated with intraclass correlation coefficient ICC (1.1) and standard error of measurements (SEM). The reliability of peak torque was good (ICC=0.93) and SEM showed low values. ICC was good for absolute RMS of rectus femoris (ICC>/=0.80), vastus medialis (ICC>/=0.88) and vastus lateralis (ICC>/=0.82) and MNF of rectus femoris (ICC>/=0.82) and vastus medialis (ICC>/=0.83). Peak torque, and MNF and RMS of rectus femoris and vastus medialis are reliable variables obtained from an isokinetic endurance test of the knee extensors.     

The involvement of <Emphasis Type="Italic">engrailed</Emphasis> and <Emphasis Type="Italic">wingless</Emphasis> during segmentation in the onychophoran <Emphasis Type="Italic">Euperipatoides kanangrensis</Emphasis> (Peripatopsidae: Onychophora) (Reid 1996)

As the putative sister group to the arthropods, onychophorans can provide insight into ancestral developmental mechanisms in the panarthropod clade. Here, we examine the expression during segmentation of orthologues of wingless (Wnt1) and engrailed, two genes that play a key role in defining segment boundaries in Drosophila and that appear to play a role in segmentation in many other arthropods. Both are expressed in segmentally reiterated stripes in all forming segments except the first (brain) segment, which only shows an engrailed stripe. Engrailed is expressed before segments are morphologically visible and is expressed in both mesoderm and ectoderm. Segmental wingless expression is not detectable until after mesodermal somites are clearly distinct. Early engrailed expression lies in and extends to both sides of the furrow that first demarcates segments in the ectoderm, but is largely restricted to the posterior part of somites. Wingless expression lies immediately anterior to engrailed expression, as it does in many arthropods, but there is no precise cellular boundary between the two expression domains analogous to the overt parasegment boundary seen in Drosophila. Engrailed stripes extend along the posterior part of each limb bud, including the antenna, while wingless is restricted to the distal tip of the limbs and the neurectoderm basal to the limbs. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The Brichos domain of prosurfactant protein C can hold and fold a transmembrane segment

Prosurfactant protein C (proSP‐C) is a 197‐residue integral membrane protein, in which the C‐terminal domain (CTC, positions 59–197) is localized in the endoplasmic reticulum (ER) lumen and contains a Brichos domain (positions 94–197). Mature SP‐C corresponds largely to the transmembrane (TM) region of proSP‐C. CTC binds to SP‐C, provided that it is in nonhelical conformation, and can prevent formation of intracellular amyloid‐like inclusions of proSP‐C that harbor mutations linked to interstitial lung disease (ILD). Herein it is shown that expression of proSP‐C (1–58), that is, the N‐terminal propeptide and the TM region, in HEK293 cells results in virtually no detectable protein, while coexpression of CTC in trans yields SDS‐soluble monomeric proSP‐C (1–58). Recombinant human (rh) CTC binds to cellulose‐bound peptides derived from the nonpolar TM region, but not the polar cytosolic part, of proSP‐C, and requires ≥5‐residues for maximal binding. Binding of rhCTC to a nonhelical peptide derived from SP‐C results in α‐helix formation provided that it contains a long TM segment. Finally, rhCTC and rhCTC Brichos domain shows very similar substrate specificities, but rhCTC^L188Q, a mutation linked to ILD is unable to bind all peptides analyzed. These data indicate that the Brichos domain of proSP‐C is a chaperone that induces α‐helix formation of an aggregation‐prone TM region.     

The Common Variant in the FTO Gene Did Not Modify the Effect of Lifestyle Changes on Body Weight: The Finnish Diabetes Prevention Study

The common single‐nucleotide polymorphism in the FTO (fat mass and obesity associated) gene is consistently associated with an increased risk of obesity. However, the knowledge of a potential modifying effect of the FTO gene on changes in body weight achieved by lifestyle intervention is limited. We examined whether the FTO gene variant (rs9939609, T/A) is associated with body weight and BMI and long‐term weight changes in the Finnish Diabetes Prevention Study (DPS). Altogether, 522 (aged 40–65 years; BMI ≥25 kg/m²) subjects with impaired glucose tolerance (IGT) were randomized to control and lifestyle intervention groups. SNP rs9939609 was genotyped from 502 subjects. At baseline, those with the AA genotype had higher BMI than subjects with other genotypes (P = 0.006). The association was observed in women (P = 0.016) but not in men. During the 4‐year follow‐up, the subjects with the AA genotype had consistently the highest BMI (P = 0.009) in the entire study population. The magnitude of weight reduction was greater in the intervention group, but the risk allele did not modify weight change in either of the groups. Our results confirm the association between the common FTO variant and BMI in a cross‐sectional setting and during the long‐term lifestyle intervention. We did not observe association between FTO variant and the magnitude of weight reduction achieved by long‐term lifestyle intervention. Based on the results from the DPS, it is unlikely that the common variant of the FTO gene affects the success of lifestyle modification on weight loss.     

Trait-based filtering from the regional species pool into local grassland communities

Aims For plants to establish in a local community from a pool of possible colonizers from the region, it must pass through a series of filters. Which of the filters is most important in this process has been much debated. In this study, we explored how species are filtered from the regional species pool into local communities. The aim was to determine if differences in species abundance and functional traits could explain which species from the regional species pool establish at the local scale and if the filtering differed between grassland communities.Methods This study took place in a cultivated landscape in southeastern Sweden. We estimated plant species abundance in 12 ex-arable field sites and 8 adjacent seminatural grassland sites and in a 100-m radius around the center of each site. We used Monte Carlo simulations to examine if species abundance and functional traits (height, seed mass, clonal abilities, specific leaf area and dispersal method) controlled the filtering of species from the regional pool into local communities.Important findings On average, only 28% of species found in the regional pool established in the ex-arable field sites and 45% in the seminatural grassland sites, indicating that the size of the regional species pool was not limiting local richness. For both grassland types, species abundance in the regional pool was positively correlated with species occurrence at the local scale. We found evidence for both species interaction filtering and dispersal limitation influencing the local assembly. Both local and regional processes were thus influencing the filtering of species from the regional species pool into local communities. In addition, the age of the communities influenced species filtering, indicating that community assembly and the importance of different filters in that process change over succession.