Thermally-induced change in the relaxation behavior of skin tissue.

Skin biothermomechanics is highly interdisciplinary, involving bioheat transfer, burn damage, biomechanics, and physiology. Characterization of the thermomechanical behavior of skin tissue is of great importance and can contribute to a variety of medical applications. However, few quantitative studies have been conducted on the thermally-dependent mechanical properties of skin tissue. The aim of the present study is to experimentally examine the thermally-induced change in the relaxation behavior of skin tissue in both hyperthermal and hypothermic ranges. The results show that temperature has great influence on the stress-relaxation behavior of skin tissue under both hyperthermal and hypothermic temperatures; the quantitative relationship that has been found between temperature and the viscoelastic parameter (the elastic fraction or fractional energy dissipation) was temperature dependent, with greatest dissipation at high temperature levels.

Transplantation of human fetal blood stem cells in the osteogenesis imperfecta mouse leads to improvement in multiscale tissue properties.

Osteogenesis imperfecta (OI or brittle bone disease) is a disorder of connective tissues caused by mutations in the collagen genes. We previously showed that intrauterine transplantation of human blood fetal stem/stromal cells in OI mice (oim) resulted in a significant reduction of bone fracture. This work examines the cellular mechanisms and mechanical bone modifications underlying these therapeutic effects, particularly examining the direct effects of donor collagen expression on bone material properties. In this study, we found an 84% reduction in femoral fractures in transplanted oim mice. Fetal blood stem/stromal cells engrafted in bones, differentiated into mature osteoblasts, expressed osteocalcin, and produced COL1a2 protein, which is absent in oim mice. The presence of normal collagen decreased hydroxyproline content in bones, altered the apatite crystal structure, increased the bone matrix stiffness, and reduced bone brittleness. In conclusion, expression of normal collagen from mature osteoblast of donor origin significantly decreased bone brittleness by improving the mechanical integrity of the bone at the molecular, tissue, and whole bone levels.

The toughness of adipose tissue: measurements and physical basis.

The measured toughness J(C) of adipose and dermal porcine tissues are 4.1 and 17 kJ m(-2), respectively, via a trouser tear test. An assessment is made of the contribution to overall toughness from the microstructural elements. The analysis suggests that the toughness of adipose tissue is determined by the collagen network that surrounds the adipocytes. The volume fraction of the interlobular septa is sufficiently low for it to make a negligible contribution to the macroscopic toughness.

Porphyrin detection in denatured cnidarian tissue extracts

Porphyrin metabolic disruption from exposure to xenobiotic contaminants such as heavy metals, dioxins, and aromatic hydrocarbons can elicit overproduction of porphyrins. Measurement of porphyrin levels, when used in conjunction with other diagnostic assays, can help elucidate an organism’s physiological condition and provide evidence for exposure to certain toxicants. A sensitive microplate fluorometric assay has been optimized for detecting total porphyrin levels in detergent solubilized protein extracts from symbiotic, dinoflagellate containing cnidarian tissues. The denaturing buffer used in this modified assay contains a number of potentially interfering components (e.g., sodium dodecyl sulfate (SDS), dithiothreitol (DTT), protease inhibitors, and chlorophyll from the symbiotic zooxanthellae), which required examination and validation. Examination of buffer components were validated for use in this porphyrin assay; while the use of a specific spectrofluorometric filter (excitation 400 ± 15 nm; emission 600 ± 20 nm) minimized chlorophyll interference. The detection limit for this assay is 10 fmol of total porphyrin per μg of total soluble protein and linearity is maintained up to 5000 fmol. The ability to measure total porphyrins in a SDS protein extract now allows a single extract to be used in multiple assays. This is an advantage over classical methods, particularly when tissue samples are limiting, as is often the case with coral due to availability and collection permit restrictions.

陆地棉抗虫基因工程研究

以陆地棉（Gossypium hirsutum L.）栽培品种新陆早4号、系550、冀资492、衡无89-30、邯93-2、冀资123等为材料，进行了组织培养及植株再生研究，建立了一套陆地棉体细胞植株再生速成体系。通过调整激素种类与比例以及改善培养条件，降低了畸形胚发生频率（从80%降为41%），并可将畸形苗转化为正常苗（转化率约为78%）;通过水培和嫁接，结合试管扦插、扩繁技术，解决了棉花生根及移栽难题，为农杆菌介导法转化棉花奠定了基础。 用绿色荧光蛋白基因（gfp）作为报告基因，构建了pBGb1m（含Bt和gfp二价基因）、pBGbf（含Bt-gfp融合基因）和pBGbfg（含Bt-gfp融合基因和gna基因）等三种植物表达载体。通过农杆菌介导法转化烟草，转基因再生植株经过荧光、虫试、PCR、Southern blot和Western blot等检测，表明三种植物表达载体能够在转基因植物中有效表达，同时，绿色荧光蛋白（GFP）的检测表现出了简便、经济、快速、可靠等优点，为大量棉花转基因苗的检测提供了一种有效方法。 采用花粉管通道法将携带细胞间隙定位信号肽的Bt基因的pBin438-S1m质粒导入棉花品种冀资492，经过田间卡那霉素筛选、虫试、PCR、PCR-Southern blot和Southern blot检测，证明Bt基因已整合至棉花基因组中，而且可能是以单拷贝形式插入。 同时，通过农杆菌介导法将三种植物表达载体（pBGb1m、pBGbf和pBGbfg）转化陆地棉栽培品种新陆早4号、冀资492、衡无89-30和邯93-2等材料，获得了大量转化再生棉株。经过PCR和PCR-Southern blot检测，转基因阳性植株为转为再生植株总数的89.45%。目前，虫试、Southern blot及Western blot正在进行之中。