Viscoelastic properties of passive skeletal muscle in compression—Cyclic behaviour

Skeletal muscle relaxation behaviour in compression has been previously reported, but the anisotropic behaviour at higher loading rates remains poorly understood. In this paper, uniaxial unconfined cyclic compression tests were performed on fresh porcine muscle samples at various fibre orientations to determine muscle viscoelastic behaviour. Mean compression level of 25% was applied and cycles of 2% and 10% amplitude were performed at 0.2–80 Hz. Under cycles of low frequency and amplitude, linear viscoelastic cyclic relaxation was observed. Fibre/cross-fibre results were qualitatively similar, but the cross-fibre direction was stiffer (ratio of 1.2). In higher amplitude tests nonlinear viscoelastic behaviour with a frequency dependent increase in the stress cycles amplitude was found (factor of 4.1 from 0.2 to 80 Hz).The predictive capability of an anisotropic quasi-linear viscoelastic model previously fitted to stress-relaxation data from similar tissue samples was investigated. Good qualitative results were obtained for low amplitude cycles but differences were observed in the stress cycle amplitudes (errors of 7.5% and 31.8%, respectively, in the fibre/cross-fibre directions). At higher amplitudes significant qualitative and quantitative differences were evident. A nonlinear model formulation was therefore developed which provided a good fit and predictions to high amplitude low frequency cyclic tests performed in the fibre/cross-fibre directions. However, this model gave a poorer fit to high frequency cyclic tests and to relaxation tests. Neither model adequately predicts the stiffness increase observed at frequencies above 5 Hz.Together with data previously presented, the experimental data presented here provide a unique dataset for validation of future constitutive models for skeletal muscle in compression.     

Polymorphisms of interferon-inducible genes OAS-1 and MxA associated with SARS in the Vietnamese population

We hypothesized that host antiviral genes induced by type I interferons might affect the natural course of severe acute respiratory syndrome (SARS). We analyzed single nucleotide polymorphisms (SNPs) of 2',5'-oligoadenylate synthetase 1 (OAS-1), myxovirus resistance-A (MxA), and double-stranded RNA-dependent protein kinase in 44 Vietnamese SARS patients with 103 controls. The G-allele of non-synonymous A/G SNP in exon 3 of OAS-1 gene showed association with SARS (p=0.0090). The G-allele in exon 3 of OAS-1 and the one in exon 6 were in strong linkage disequilibrium and both of them were associated with SARS infection. The GG genotype and G-allele of G/T SNP at position -88 in the MxA gene promoter were found more frequently in hypoxemic group than in non-hypoxemic group of SARS (p=0.0195). Our findings suggest that polymorphisms of two IFN-inducible genes OAS-1 and MxA might affect susceptibility to the disease and progression of SARS at each level.     

Large-scale production of a therapeutic protein in transgenic tobacco plants: effect of subcellular targeting on quality of a recombinant dog gastric lipase

A recombinant dog gastric lipase with therapeutic potential for the treatment of exocrine pancreatic insufficiency was expressed in transgenic tobacco plants. We targeted the protein using two different signal sequences for either vacuolar retention or secretion. In both cases, an active glycosylated recombinant protein was obtained. The recombinant enzymes and the native enzyme displayed similar properties including acid resistance and acidic optimum pH. The proteolytic maturation and the specific activity of the recombinant proteins, however, were found to be dependent on subcellular compartmentalization. Expression levels of recombinant dog gastric lipase were about 5% and 7% of acid extractable plant proteins for vacuolar retention and secretion respectively. This expression system already has allowed the production of tens of grams of purified lipase through open-field culture of transgenic tobacco plants.     

Evolutionary relationships in thePodalyrieae andLiparieae (Fabaceae) based on morphological, cytological, and chemical evidence

Taxonomic relationships amongst the genera of the southern African tribesPodalyrieae andLiparieae are discussed. Data gained from morphological, cytological and chemical investigations are analyzed cladistically to determine relationships. The genusCadia (tribeSophoreae) is included in the investigation to establish whether it should be transferred to thePodalyrieae. The results clearly indicate that thePodalyrieae andLiparieae are monophyletic and that they should be united, but thatHypocalyptus andCadia should be excluded. Within the monophyletic group, there are two distinct subclades each supported by three apomorphies. The results also show that there is a strong sister relationship betweenAmphithalea andCoelidium. In the taxonomic treatment theLiparieae are placed into synonymy under thePodalyrieae and two subtribes are recognized. A key to the genera in the tribe is given, followed by a synopsis of the genera.     

Efficient removal of LoxP-flanked genes by electroporation of Cre-recombinase mRNA

Introduction of Cre-recombinase in target cells is currently achieved by transfection of plasmid DNA or by viral-mediated transduction. However, efficiency of non-viral DNA transfection is often low in many cell types, and the use of viral vectors for transduction implies a more complex and laborious manipulation associated with safety issues. We have developed a non-viral non-DNA technique for rapid and highly efficient excision of LoxP-flanked DNA sequences based on electroporation of in vitro transcribed mRNA encoding Cre-recombinase. A K562-DSRed[EGFP] cell line was developed in order to measure Cre-mediated recombination by flow cytometric analysis. These cells have a stable integrated DSRed reporter gene flanked by two LoxP sites, and an EGFP reporter gene, which could only be transcribed when the coding sequence for DSRed was removed. The presented data show recombination efficiencies, as measured by appearance of EGFP-fluorescence, of up to 85% in Cre-recombinase mRNA-electroporated K562-DSRed[EGFP] cells. In conclusion, mRNA electroporation of Cre-recombinase is a powerful, safe, and clinically applicable alternative to current technologies used for excision of stably integrated LoxP-flanked DNA sequences.     

Influence of ploidy level on morphology,growth and drought susceptibility in <Emphasis Type="Italic">Spathiphyllum wallisii</Emphasis>

In this study, we analysed morphological, anatomical and physiological effects of polyploidisation in Spathiphyllum wallisii in order to evaluate possible interesting advantages of polyploids for ornamental breeding. Stomatal density was negatively correlated with increased ploidy level. Stomatal size increased in polyploids. Tetraploid Spathiphyllum plants had more ovate and thicker leaves. The inflorescence of tetraploids had a more ovate and thicker spathum, a more cylindrical spadix and a thicker but shorter flower stalk. Biomass production of the tetraploids was reduced, as expressed by lower total dry weights, and tetraploids produced fewer shoots and leaves compared with their diploid progenitors. Furthermore, tetraploid Spathiphyllum plants were more resistant to drought stress compared with diploid plants. After 15 days of drought stress, diploids showed symptoms of wilting, while the tetraploids showed almost no symptoms. Further, measurements of stomatal resistance, leaf water potential, relative water content and proline content indicated that the tetraploid genotypes were more resistant to drought stress compared with the diploids.     

Identification of Paenibacillus larvae to the subspecies level: an obstacle for AFB diagnosis

This study was initially aimed at developing a PCR-test to differentiate between the pathogenic agent of American foulbrood (Paenibacillus larvae subsp. larvae) and powdery-scale disease (P. larvae subsp. pulvifaciens) of the honeybee. The test was based on the "insert of clone 9" (iC9), referring to a cloned 1.9 kB HaeIII fragment that occurs only in the P. larvae subsp. larvae reference strains and possibly correlates with American foulbrood virulence. It was shown that an iC9-based PCR-test discriminates between the BCCM/LMG reference strains of both subspecies. However, the screening of 179 Belgian field strains revealed five isolates that gave no iC9-based amplicon, thus rather resembling to P. larvae subsp. pulvifaciens. In addition, they all produced acid from mannitol, a characteristic previously assigned to the pulvifaciens subspecies. Because the reference strains gave conflicting data, this carbohydrate acidification was not conclusive. Therefore, the exact taxonomic position of the five retained strains was determined by a polyphasic approach using SDS-PAGE, AFLP, and ERIC-based PCR. Four iC9-negative field strains could be identified as P. larvae subsp. larvae; the taxonomic position of the fifth field strain remained ambiguous. The latter was provisionally classified as a subspecies pulvifaciens strain on the basis of SDS-PAGE. The present paper demonstrates the existence of field strains that do not fit well in the subdivision of the species P. larvae into two subspecies. Knowing that only one of both subspecies represents the pathogenic agent of AFB, this is a serious obstacle for the diagnosis of this honeybee disease.     

Assessment of tibial stiffness by vibration testing in situ--I. Identification of mode shapes in different supporting conditions

Vibrational methods to monitor fracture healing, the BRA and the IFR, are compared under different supporting conditions, excitation technique and signal processing. Mode shapes are identified by modal analysis. A wet excised human tibia and an amputation specimen are investigated. Excitation technique and signal processing caused only minor differences in the resonance frequencies. The supporting conditions had an important influence on the single bending modes changing both mode-shapes and frequencies. Thus the BRA-splint imposed a node at the malleolus. Modal analysis revealed the following modes in the two supporting conditions: BRA-splint: A 'rigid body' mode of 165 Hz in the sagittal plane. A single bending mode of 315 Hz close to the sagittal plane. IFR-hanging leg: A 'rigid-body' mode of 167 Hz close to the sagittal plane. Two single bending modes ('free-free'), a mode of 303 Hz close to the frontal plane and a mode of 470 Hz in the sagittal plane.