Myosin filament sliding through the Z-disc relates striated muscle fibre structure to function

Striated muscle contraction requires intricate interactions of microstructures. The classic textbook assumption that myosin filaments are compressed at the meshed Z-disc during striated muscle fibre contraction conflicts with experimental evidence. For example, myosin filaments are too stiff to be compressed sufficiently by the muscular force, and, unlike compressed springs, the muscle fibres do not restore their resting length after contractions to short lengths. Further, the dependence of a fibre''s maximum contraction velocity on sarcomere length is unexplained to date. In this paper, we present a structurally consistent model of sarcomere contraction that reconciles these findings with the well-accepted sliding filament and crossbridge theories. The few required model parameters are taken from the literature or obtained from reasoning based on structural arguments. In our model, the transition from hexagonal to tetragonal actin filament arrangement near the Z-disc together with a thoughtful titin arrangement enables myosin filament sliding through the Z-disc. This sliding leads to swivelled crossbridges in the adjacent half-sarcomere that dampen contraction. With no fitting of parameters required, the model predicts straightforwardly the fibre''s entire force–length behaviour and the dependence of the maximum contraction velocity on sarcomere length. Our model enables a structurally and functionally consistent view of the contractile machinery of the striated fibre with possible implications for muscle diseases and evolution.     

Functional Anatomy: A Taxonomic Proposal

It is argued that medical science requires a classificatory system that (a) puts functions in the taxonomic center and (b) does justice ontologically to the difference between the processes which are the realizations of functions and the objects which are their bearers. We propose formulae for constructing such a system and describe some of its benefits. The arguments are general enough to be of interest to all the life sciences.     

The telomeric region of BTA18 containing a potential QTL region for health in cattle exhibits high similarity to the HSA19q region in humans

We have applied a targeted physical mapping approach, based on the isolation of bovine region-specific large-insert clones using homologous human sequences and chromosome microdissection, to enhance the physical gene map of the telomeric region of BTA18 and to prove its evolutionary conservation. The latter is a prerequisite to exploit the dense human gene map for future positional cloning approaches. Partial sequencing and homology search were used to characterize 20 BACs targeted to the BTA18q2.4-q2.6 region. We used fluorescence in situ hybridization (FISH) to create physical maps of 11 BACs containing 15 gene loci; these BACs served as anchor loci. Using these approaches, 12 new gene loci (CKM, STK13, PSCD2, IRF3, VASP, ACTN4, ITPKC, CYP2B6, FOSB, DMPK, MIA, SIX5) were assigned on BTA18 in the bovine cytogenetic map. A resolved physical map of BTA18q2.4-q2.6 was developed, which encompasses 28 marker loci and a comparative cytogenetic map that contains 15 genes. The mapping results demonstrate the high evolutionary conservation between the telomeric region of BTA18q and HSA19q.     

A preliminary histological investigation of gall induction in an unconventional galling system

In an unusual case involving a candidate biological control agent, the histologically complex stem galls of the weevil, Rhinusa pilosa (Coleoptera: Curculionidae) on yellow toadflax (Linaria vulgaris), are rapidly induced during oviposition and reach full size by larval hatch. To investigate gall induction, the oviposition behavior of R. pilosa was described. We experimentally disrupted ovipositing weevils at three key points in the oviposition sequence and compared host-plant tissue responses post disruption, to what occurs during normal gall induction using histological methods. De novo xylem production, intercellular spaces in the cortex, and hyperplasia and hypertrophy of the procambium and pith parenchyma surrounding the egg were some of the tissue- and cellular-level modifications observed only 3?C5?days after normal oviposition. Normal gall development was not observed after any of the oviposition disruption treatments, although some of the cellular and tissue responses resembled those found after undisrupted oviposition. Feeding by the female during oviposition canal formation induced wound meristem and callus tissue formation, but no other modifications consistent with gall formation. When females were disrupted about 20?s into oviposition, a homogenously dense substance was observed, which was suspected to be ovipositional fluid. There was minor stem swelling 10?days later and histologically, periclinal cell divisions, de novo xylem, and pith cells with numerous stained plastids were observed as in normal gall development, thus suggesting that ovipositional fluid plays a role in gall induction.     

Septate-like junctions between cells of the immune system in vivo.

Septate-like junctions between lymphocytes, lymphocytes and macrophages, and macrophages were observed in cellular capsules surrounding larvae of the tapeworm Taenia crassiceps after intraperitoneal inoculation into immunized mice. The morphology of the junctions found in vivo is similar to that reported for septate-like junctions between cells of the immune system in vitro. These findings support the possibility that septate-like junctions may be involved in functional interactions between cells of the immune system both in vivo and in vitro.     

Metabolic syndrome in Yup'ik Eskimos: the Center for Alaska Native Health Research (CANHR) Study

Objective: This study investigated the prevalence of metabolic syndrome and its defining components among Yup'ik Eskimos. Research Methods and Procedures: A cross‐sectional study design that included 710 adult Yup'ik Eskimos ≥18 years of age residing in 8 communities in Southwest Alaska. The prevalence of metabolic syndrome was determined using the recently updated Adult Treatment Panel III criteria. Results: The prevalence of metabolic syndrome in this study cohort was 14.7%, and varied by sex with 8.6% of the men and 19.8% of the women having metabolic syndrome. This is lower than the prevalence of 23.9% in the general U.S. adult population. The most common metabolic syndrome components/risk factors were increased waist circumference and elevated blood glucose. High‐density lipoprotein (HDL) cholesterol levels in Yup'ik Eskimos were significantly higher, and triglycerides lower than levels reported in National Health and Nutritional Examination III. Discussion: Compared with other populations, metabolic syndrome is relatively uncommon in Yup'ik Eskimos. The higher prevalence among Yup'ik women is primarily explained by their large waist circumference, suggesting central body fat accumulation. Further increases in metabolic syndrome risk factors among Yup'ik Eskimos could lead to increases in the prevalence of type 2 diabetes and cardiovascular disease, once rare in this population.     

How to Handle Speciose Clades? Mass Taxon-Sampling as a Strategy towards Illuminating the Natural History of Campanula (Campanuloideae)

Background

Speciose clades usually harbor species with a broad spectrum of adaptive strategies and complex distribution patterns, and thus constitute ideal systems to disentangle biotic and abiotic causes underlying species diversification. The delimitation of such study systems to test evolutionary hypotheses is difficult because they often rely on artificial genus concepts as starting points. One of the most prominent examples is the bellflower genus Campanula with some 420 species, but up to 600 species when including all lineages to which Campanula is paraphyletic. We generated a large alignment of petD group II intron sequences to include more than 70% of described species as a reference. By comparison with partial data sets we could then assess the impact of selective taxon sampling strategies on phylogenetic reconstruction and subsequent evolutionary conclusions.

Methodology/Principal Findings

Phylogenetic analyses based on maximum parsimony (PAUP, PRAP), Bayesian inference (MrBayes), and maximum likelihood (RAxML) were first carried out on the large reference data set (D680). Parameters including tree topology, branch support, and age estimates, were then compared to those obtained from smaller data sets resulting from “classification-guided” (D088) and “phylogeny-guided sampling” (D101). Analyses of D088 failed to fully recover the phylogenetic diversity in Campanula, whereas D101 inferred significantly different branch support and age estimates.

Conclusions/Significance

A short genomic region with high phylogenetic utility allowed us to easily generate a comprehensive phylogenetic framework for the speciose Campanula clade. Our approach recovered 17 well-supported and circumscribed sub-lineages. Knowing these will be instrumental for developing more specific evolutionary hypotheses and guide future research, we highlight the predictive value of a mass taxon-sampling strategy as a first essential step towards illuminating the detailed evolutionary history of diverse clades.     

Substrate affinity in PGM1, PGM2, and PGM3 isozymes

Summary An easy method for routine detection of PGM₁, PGM₂, and PGM₃ isozymes is given. Differences in substrate affinity are discussed. Gene products pgm₁ can be differentiated from gene products pgm₃ by cofactor requirement.     

Using the Hard, Randy, and Rittler Test to Evaluate Color Vision in Capuchins (Cebus libidinosus)

The identification of color vision types in primates is fundamental to understanding the evolution and biological function of color perception. The Hard, Randy, and Rittler (HRR) pseudoisochromatic test categorizes human color vision types successfully. Here we provide an experimental setup to employ HRR in a nonhuman primate, the capuchin (Cebus libidinosus), a platyrrhine with polymorphic color vision. The HRR test consists of plates with a matrix composed of gray circles that vary in size and brightness. Differently colored circles form a geometric shape (X, O, or Δ) that is discriminated visually from the gray background pattern. The ability to identify these shapes determines the type of dyschromatopsy (deficiency in color vision). We tested six capuchins in their own cages under natural sunlight. The subjects chose between two HRR plates in each trial: one with the gray pattern only and the other with a colored shape, presented on the left or right side at random. We presented the test 40 times and calculated the 95?% confidence limits for chance performance based on the binomial test. We also genotyped all subjects for exons 3 and 5 of the X-linked opsin genes. The HRR test diagnosed two subjects as protan dichromats (missing or defective L-cone), three as deutan dichromats (missing or defective M-cone), and one female as trichromat. Genetic analysis supported the behavioral data for all subjects. These findings show that the HRR test can be applied to diagnose color vision in nonhuman primates.