Contraction and stiffness changes in collagenous arm ligaments of the stalked crinoid Metacrinus rotundus (Echinodermata)

Shortening and stiffness were measured simultaneously in the aboral ligament of arms of sea lilies. Arm pieces were used from which oral tissues (including muscles) were removed, leaving only collagenous ligaments connecting arm ossicles. Chemical stimulation by means of artificial seawater with an elevated concentration of potassium caused both a bending movement and stiffness changes (either softening or stiffening). The movement lasted for 1.5-10 min, and bent posture was maintained. The observation that contraction was not necessarily associated with softening provided evidence against the hypothesis that the shortening of the aboral ligaments was driven by the elastic components that had been charged by the oral muscles and released their strain energy at the softening of the aboral ligaments. The speed of ligamental shortening was slower by at least one order of magnitude than that of muscles. Acetylcholine (10(-5)-10(-3) M) caused both contraction and softening. We conclude that the aboral ligament shows two mechanical activities based on different mechanisms: one is active contraction and the other is connective tissue catch in which passive mechanical properties show mutability. We suggest that there is neural coordination between the two mechanisms.     

Expression of genes for gelatinases and tissue inhibitors of metalloproteinases in periodontal tissues during orthodontic tooth movement

Orthodontic tooth movement progresses by a combination of periodontal ligament (PDL) tissue and alveolar bone remodeling processes. Besides the remodeling of alveolar bone around the moving teeth, the major extracellular matrix (ECM) components of PDLs, collagens, are degenerated, degraded, and restructured. Matrix metalloproteinases (MMPs) and their specific inhibitors, tissue inhibitors of metalloproteinases (TIMPs), act in a co-ordinated fashion to regulate the remodeling of periodontal tissues. We hypothesized that the expression levels of the genes for MMP-2, MMP-9, and TIMPs 1–3 are increased transiently in the periodontal tissue during orthodontic tooth movement. To test this hypothesis, we employed an animal model of tooth movement using rats, as well as in situ hybridization to analyze the expression levels of Mmp-2, Mmp-9, and Timps 1-3. The expression levels of these genes increased transiently in cells of periodontal tissues, which include cementoblasts, fibroblasts, osteoblasts, and osteoclasts, at the compression side of the moving teeth. The transient increases in gene expression at the tension side were mainly limited to osteoblasts and cementoblasts. In conclusion, the expression levels of Mmp-2, Mmp-9, and Timps 1-3 increase transiently during orthodontic tooth movement at both the tension and compression sides. The expression of these genes is regulated differentially in the periodontal tissue of the tension side and compression side. This altered pattern of gene expression may determine the rate and extent of remodeling of the collagenous ECM in periodontal tissues during orthodontic tooth movement.     

Larval development and settlement of a whale barnacle

Larval development and settlement of whale barnacles have not previously been described, unlike intertidal barnacles. Indeed, the mechanisms of the association between barnacles and whales have not been studied. Here we describe the larval development and settlement of the whale barnacle, Coronula diadema, and possible involvement of a cue from the host in inducing larval settlement. Eight-cell stage embryos were collected from C. diadema on a stranded humpback whale, incubated in filtered seawater for 7 days, and nauplius larvae hatched out. When fed with Chaetoceros gracilis, the nauplii developed to stage VI, and finally metamorphosed to the cypris stage. The larval development looked similar to that of intertidal barnacles with planktotrophic larval stages. The cyprids did not settle in normal seawater, but did settle in polystyrene Petri dishes when incubated in seawater with a small piece of skin tissue from the host whale. This strongly suggests the involvement of a chemical cue from the host whale tissue to induce larval settlement.     

A new synbiotic, Lactobacillus casei subsp. casei together with dextran, reduces murine and human allergic reaction

We studied the development of atopic dermatitis-like skin lesions in NC/Nga mice and the allergic symptoms and blood patterns of healthy volunteers during the cedar (Cryptomeria japonica) pollen season in Japan following oral administration of a new synbiotic, Lactobacillus casei subsp. casei together with dextran. The combination of L. casei subsp. casei and dextran significantly decreased clinical skin severity scores and total immunoglobulin E levels in sera of NC/Nga mice that had developed picryl chloride-induced and Dermatophagoides pteronyssinus crude extract-swabbed atopic dermatitis-like skin lesions. During the most common Japanese cedar pollen season, synbiotic L. casei subsp. casei and dextran in humans led to no significant changes in total nasal and ocular symptom scores, in the levels of cedar pollen-specific immunoglobulin E, interferon-gamma and thymus and activation regulated chemokine or in the number of eosinophils in sera, whereas the placebo group showed a tendency for increased levels of cedar pollen-specific immunoglobulin E, thymus and activation regulated chemokine and number of eosinophils, and a decrease in interferon-gamma levels. Thus, the oral administration of synbiotic L. casei subsp. casei together with dextran appears to be an effective supplement for the prevention and treatment of allergic reactions.     

On the respiratory mechanism during underwater oviposition in a damselfly Calopteryx cornelia Selys

Calopteryx cornelia females oviposit almost exclusively underwater in forest streams. Field observation showed that the duration of uninterrupted submerged oviposition ranged between 20 and 120 min and the number of eggs laid was linearly related to the time spent underwater. By holding a damselfly under water in a small jar, we measured the maximum 'submergence potential', which was defined as the time elapsed between placing the insect underwater and asphyxiation. A series of experiments showed that there was no gender difference in the submergence potential. This was about 120 min if a damselfly was allowed to change its position while under water. The submergence potential was shorter if the damselflies were kept motionless, if air bubbles trapped on the wing surfaces were removed by coating with Vaseline or if the water was hypoxic. By contrast, submergence potential was longer if a part of the wings were kept above the water surface, or if the water was agitated using a magnetic stirrer. These results suggest that ovipositing C. cornelia females depend for oxygen on the physical-gill action of the thin air layer trapped on the body and wing surfaces. Respiration capacity under water is not likely to be a limiting factor for ovipositing females during the production of a single clutch.     

Mhc class I genes of the cichlid fish Oreochromis niloticus

In terms of number of species, perciform (perch-like) fishes are one of the most diversified groups of modern vertebrates. Within this group, the family Cichlidae is best known for its spectacular adaptive radiation in the great lakes of East Africa. The molecular tool kit used in the study of this radiation includes the major histocompatibility complex (Mhc) genes. To refine this tool, information about the organization of the Mhc regions is badly needed. In this study, the first step was taken toward providing such information for the Mhc class one regions of Oreochromis niloticus, a representative species of the tilapiine branch of the Cichlidae, for which good bacterial artificial chromosome library is available. Screening of the library with class I gene probes led to the identification and isolation of 31 class-I-positive clones. Sequencing of one of these clones and partial characterization of the remaining clones for the presence of class I exons resulted in the construction of two contigs representing the class I region of this species as well as identification of seven additional class-I-positive singleton clones. The O. niloticus genome was shown to contain at least 28 class I genes or gene fragments. The shorter of the two contigs was approximately 330 kb long and contained eight class I genes/gene fragments; the longer contig encompassed 1,200 kb of sequence and contained minimally 17 class I genes/gene fragments; three additional class I genes were found to be borne by a clone that might be part of the shorter contig. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. This work had been carried out in part at the Max-Planck-Institut für Biologie, Abteilung Immungenetik, Tübingen, Germany (A.S., R.D., N.T., S.S., and J.K.). The sequences reported in this paper have been deposited in the GenBank database (accession nos. AB270803–AB270897).     

Mathematical description of stress relaxation of bovine femoral cortical bone

In 1993 we proposed an empirical formula for describing the relaxation modulus of cortical bone based on the results of stress relaxation experiments performed for 1 x 10(5) sec: [E(t) = E0{A exp[ -(t/tau1)beta] + (1 - A) exp(-t/tau2)}, (0 < A, beta <1 and tau1 < tau2) where E0 is the initial value of the relaxation modulus, A is the portion of the first term, tau1 and tau2 are characteristic relaxation times, and beta is a shape factor [Sasaki et al., J. Biomechanics 26 (1993), 1369]. Although the relaxation properties of bone under various external conditions were described well by the above equation, recent experimental results have indicated some limitations in its application. In order to construct an empirical formula for the relaxation modulus of cortical bone that has a high degree of completeness, stress relaxation experiments were performed for 6 x 10(5) seconds. The second term in the equation was determined as an apparently linear portion in a log E(t) vs t plot at t>1 x 10(4) sec. The same plot for experiments performed for 6 x 10(5) seconds revealed that the linear portion corresponding to the second term was in fact a curve with a large radius of curvature. On the basis of this fact, we proposed a second improved empirical equation E(t) = E0{A exp [ -(t/tau1)beta] + (1 - A) exp[-(t/tau2)gamma]}, (0相似文献   

A three-dimensional FRET analysis to construct an atomic model of the actin-tropomyosin-troponin core domain complex on a muscle thin filament

It is essential to know the detailed structure of the thin filament to understand the regulation mechanism of striated muscle contraction. Fluorescence resonance energy transfer (FRET) was used to construct an atomic model of the actin-tropomyosin (Tm)-troponin (Tn) core domain complex. We generated single-cysteine mutants in the 167-195 region of Tm and in TnC, TnI, and the β-TnT 25-kDa fragment, and each was attached with an energy donor probe. An energy acceptor probe was located at actin Gln41, actin Cys374, or the actin nucleotide-binding site. From these donor-acceptor pairs, FRET efficiencies were determined with and without Ca(2+). Using the atomic coordinates for F-actin, Tm, and the Tn core domain, we searched all possible arrangements for Tm or the Tn core domain on F-actin to calculate the FRET efficiency for each donor-acceptor pair in each arrangement. By minimizing the squared sum of deviations for the calculated FRET efficiencies from the observed FRET efficiencies, we determined the location of Tm segment 167-195 and the Tn core domain on F-actin with and without Ca(2+). The bulk of the Tn core domain is located near actin subdomains 3 and 4. The central helix of TnC is nearly perpendicular to the F-actin axis, directing the N-terminal domain of TnC toward the actin outer domain. The C-terminal region in the I-T arm forms a four-helix-bundle structure with the Tm 175-185 region. After Ca(2+) release, the Tn core domain moves toward the actin outer domain and closer to the center of the F-actin axis.     

Radiocesium distribution in the tissues of Japanese black beef heifers fed fallout-contaminated roughage due to the fukushima daiichi nuclear power station accident

This study examined the accumulation and tissue distribution of radioactive cesium nuclides in Japanese Black beef heifers raised on roughage contaminated with radioactive fallout due to the accident at the Fukushima Daiichi Nuclear Power Station on March 2011. Radiocesium feeding increased both (134)Cs and (137)Cs levels in all tissues tested. The kidney had the highest level and subcutaneous adipose had the lowest of radioactive cesium in the tissues. Different radioactive cesium levels were not found among parts of the muscles. These results indicate that radiocesium accumulated highly in the kidney and homogenously in the skeletal muscles in the heifers.     

Characterization of a bacterial laminaribiose phosphorylase

Bacterial laminaribiose phosphorylase (LBP(bac)) was first identified and purified from cell-free extract of Paenibacillus sp. YM-1. It phosphorolyzed laminaribiose into α-glucose 1-phosphate and glucose, but did not phosphorolyze other glucobioses. It slightly phosphorolyzed laminaritriose and higher laminarioligosaccharides. The specificity of the degree of polymerization of the substrate was clearly different from that of the enzyme of Euglena gracilis (LBP(Eug)): LBP(bac) was more specific to laminaribiose than LBP(Eug). It showed acceptor specificity in reverse phosphorolysis similar to LBP(Eug). Cloning of the gene encoding LBP(bac) (lbpA) has revealed that LBP(bac) is a member of the glucoside hydrolase family 94, which includes cellobiose phosphorylase, cellodextrin phosphorylase, and N,N'-diacetylchitobiose phosphorylase. The genes that encode the components of an ATP-binding cassette sugar transporter specific to laminarioligosaccharides were identified upstream of lbpA, suggesting that the role of LBP(bac) is to utilize laminaribiose generated outside the cell. This role is different from that of LBP(Eug), which participates in the utilization of paramylon, the intracellular storage 1,3-β-glucan.