A finite element based method to determine the properties of planar soft tissue.

A finite element based method to determine the incremental elastic material properties of planar membranes was developed and evaluated. The method is applicable to tissues that exhibit inhomogeneity, geometric and material nonlinearity, and anisotropy. Markers are placed on the tissue to form a four-node quadrilateral element. The specimen is loaded to an initial reference state, then three incremental loading sets are applied and the nodal displacements recorded. One of these loadings must include shear. These data are used to solve an over-determined system of equations for the tangent stiffness matrix. The method was first verified using analytical data. Next, data obtained from a latex rubber sheet were used to evaluate experimental procedures. Finally, experiments conducted on preconditioned rat skin revealed nonlinear orthotropic behavior. The vector norm comparing the applied and calculated nodal force vectors was used to evaluate the accuracy of the solutions.     

Distribution of gamma-glutamyl transpeptidase in the mouse epididymis and its response to acivicin

gamma-Glutamyl transpeptidase (gamma-GT), its substrate (GSH) and hydrolytic product (L-glutamic acid) were measured biochemically in mouse reproductive tissues. The epididymal caput and seminal vesicles showed the highest specific activities of gamma-GT, while GSH and L-glutamic acid were widely distributed in all tissues. Histochemically, gamma-GT displayed a strong apical and supranuclear reaction and a moderate basal activity in the ductuli efferents, a weak luminal reaction in the first, a moderate apical reaction in the second and a strong apical and supranuclear reaction in the third segment of the epididymal caput. In the epididymal corpus and cauda, the gamma-GT reaction was confined to the tubular lumina but an apical reaction was also present in the cauda. The daily administration of acivicin (12 mg/kg body weight), an irreversible inhibitor of gamma-GT, for 14 days resulted in a 60% suppression of the enzyme activity in the epididymal caput, while the gamma-GT inhibition in the kidney was greater than 95%. The treatment caused no change in the activity of alanyl aminopeptidase. Histochemically, the basal and supranuclear gamma-GT activities in the ductuli efferents and the third epididymal segment were suppressed, but the apical reactions were maintained. The in-vivo suppression of epididymal gamma-GT activity may have implications in the control of post-testicular sperm maturation.     

Functional structure of the carpal and ventral vibrissae of the squirrel (Sciurus vulgaris)

A study is made of the histology, distribution and ultrastructure of nerve-organs in the carpal and ventral sinus hairs of the squirrel Sciurus vulgaris L. These sinus hairs were found to be typical tactile hairs. Their situation on the inner surfaces of the forelimbs, and on the ventral body wall is assumed to be useful during climbing. Five different types of nerve end-organs were found:
1. Ring-shaped end-organs, especially in the ring sinus, associated with certain cells in connectivetissue and in many cases also anchored to the hair follicle.
2. Merkelcells in the basal cell layer of the outer root sheath at the level of the ring sinus.
3. Lanceolate end-organs between the glassy membrane and the connective tissue of the ringwulst and betweenthese in the upper part of the ring sinus.
4. Encapsulated end-organs in the cavernous sinus.
5. Free thin nerveendings.     

The use of H2 antagonists in treating and preventing NSAID-induced mucosal damage

Pain affects the quality of life for millions of individuals and is a major reason for healthcare utilization. As populations age, medical personnel will need to manage more and more patients suffering from pain associated with degenerative and inflammatory musculoskeletal disorders. Nonsteroidal anti-inflammatory drugs (NSAIDs) are an effective treatment for both acute and chronic musculoskeletal pain; however, their use is associated with potentially significant gastrointestinal (GI) toxicity. Guidelines suggest various strategies to prevent problems in those at risk for NSAID-associated GI complications. In this article, we review the data supporting one such strategy - the use of histamine type-2 receptor antagonists (H2RAs) - for the prevention of GI adverse events in NSAID users. Older studies suggest that high-dose H2RAs are effective in preventing upper GI ulcers and dyspepsia. This suggestion was recently confirmed during clinical trials with a new ibuprofen/famotidine combination that reduced the risk of ulcers by 50% compared with ibuprofen alone.     

A comparison of established and new approaches in ovine and bovine nuclear transfer

Several breakthroughs in nuclear transfer research were first achieved in sheep, although cattle soon became the main livestock species of interest. However, sheep still offer significant advantages both in basic and applied research. With increased interest in cloning of livestock, new approaches have been developed for both sheep and cattle nuclear transfer technology. These include methods for zona-free nuclear transfer that can be performed with or without the use of micromanipulator. Here we describe four different nuclear transfer methods including the traditional micromanipulation-assisted method in sheep, zona-free method in sheep in which the order of enucleation and nucleus delivery have been reversed ("reverse-order" cloning) and zona free manual cloning methods ("hand-made cloning") for embryonic and somatic cloning in cattle. The purpose of this paper is to encourage people to familiarize themselves with these different methods available and to help them choose and test the method most suitable for their particular circumstances.     

Improved in vitro development rates of sheep somatic nuclear transfer embryos by using a reverse-order zona-free cloning method

This paper describes a modified zona-free cloning protocol for examining the effects of short-term exposure of donor nuclei to maternal chromosomal components and associated factors. In vitro matured zona-free sheep oocytes were enucleated by micromanipulator-assisted aspiration either before or after fusion with adult fibroblast or granulosa donor cells. Subsequent kinetics of donor nuclei and maternal chromatin as well as in vitro embryo development rates were recorded. The effect of an additional activation stimulus in connection with the reverse-order cloning (fusion before enucleation) and the feasibility of manual enucleation by metal blade were also studied. As a result of the simultaneous fusion and activation, most donor nuclei remained in interphase but swelled in size. Maternal chromosomes reached anaphase II-telophase II stages within 1-2 h of activation, effectively facilitating telophase enucleation with both the micromanipulator-assisted aspiration and manual bisection. A significantly higher development rate to the blastocyst stage was achieved with the reverse-order protocol, suggesting further investigation into the possible role of oocyte nucleus-associated factors in reprogramming is warranted. Overall, the reverse-order zona-free cloning method was efficient in the production of transferable cloned sheep blastocysts and may offer yet another choice of methodology in the practical application of nuclear transfer technology.     

Factors influencing the output of an implantable force transducer

The objective of this study was to evaluate the performance of the Arthroscopically Implantable Force Probe (AIFP; MicroStrain, Burlington VT) for measuring force in a patellar tendon graft. Transducer drift, reproducibility of output due to the number of loading cycles and device location, and sensitivity to the tendon cross-sectional area were investigated. The AIFP was initialized, and then implanted into five human patellar tendon grafts three times; twice within the same location and once in a different location. The tendons were cyclically loaded in uniaxial tension for 500 cycles in each insertion site. The AIFP was then removed from the tendon and the baseline output was remeasured. It was determined that transducer drift was negligible. The relationship between the tensile load applied to the graft and AIFP output was quadratic and specimen dependent. The cyclic load response of the tendon-AIFP interface demonstrated a 24.9% decrease over the first 20 loading cycles, and subsequent cycling yielded relatively reproducible output. The output of the transducer varied when it was removed from the tendon and then reimplanted in the same location (range 3.7-109. 4% error), as well as in the second location (range 1.5-202.8% error). No correlation was observed between the cross-sectional area of the tendon and transducer output. This study concludes that implantable force probes should be used with caution and calibrated without removing the transducer from the graft.     

Telomere length status of somatic cell sheep clones and their offspring

This study was carried out to determine the telomere length status of sheep clones and their offspring, and to examine telomere dynamics and chromosomal abnormalities in culture propagated donor cells. Skin samples were collected from somatic cell nuclear transfer-derived sheep clones, and three of their progeny generated by natural mating. Samples were collected from control animals (n = 35), spanning in age from 1 month to 36 months of age. Genomic DNA was extracted from cell/tissue samples and their telomere lengths were assessed by terminal restriction fragment (TRF) analysis. Results revealed: that (a) sheep clones derived from cultured somatic cells have shortened telomere lengths compared to age-matched controls; (b) the offspring derived from natural mating between clones had normal telomere lengths compared to their age-matched counterparts; and donor cell cultures beyond 20 population doublings had significantly (P < 0.05) shortened telomeres and exhibited a higher numerical and structural chromosomal abnormalities.     

The role of organic matter and microbial community controlling nitrate reduction under elevated ferrous iron concentrations in boreal lake sediments

Hydrobiologia - The nitrogen availability, that affects the greenhouse gas emission and the trophic level of lakes, is controlled mainly by microbial processes. We measured in a boreal nitrate and...