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91.
A variational constitutive model for soft biological tissues 总被引:1,自引:0,他引:1
In this paper, a fully variational constitutive model of soft biological tissues is formulated in the finite strain regime. The model includes Ogden-type hyperelasticity, finite viscosity, deviatoric and volumetric plasticity, rate and microinertia effects. Variational updates are obtained via time discretization and pre-minimization of a suitable objective function with respect to internal variables. Genetic algorithms are used for model parameter identification due to their suitability for non-convex, high dimensional optimization problems. The material behavior predicted by the model is compared to available tests on swine and human brain tissue. The ability of the model to predict a wide range of experimentally observed behavior, including hysteresis, cyclic softening, rate effects, and plastic deformation is demonstrated. 相似文献
92.
福尔马林固定白暨豚标本DNA提取及其遗传多样性的初步研究 总被引:4,自引:0,他引:4
福尔马林固定标本是宝贵的遗传资源,但是如何有效利用其中的遗传信息一直存在问题。本文尝试从标本预处理、消化、PCR扩增各方面综合考虑和优化改进,成功提取并扩增21头福尔马林固定白暨豚标本线粒体DNA控制区410bp片段。采用了3种预处理方法尽量去除固定标本中残存的甲醛,从试验结果来看,从酒精梯度 临界点干燥处理的标本中提取的DNA在扩增时具有明显优势。通过蛋白酶K消化过程中对于酶的浓度、温浴时间的比较试验,发现随着采用大幅提高酶浓度、延长消化时间等高强度的蛋白酶消化操作后,DNA的质量和产量均得到显著提高。针对标本DNA降解严重的特点,设计特异性好且长度合适的引物以及使用巢式引物扩增,均提高了标本DNA扩增的特异性和灵敏度。通过对所测得的2l头白暨豚线粒体DNA控制区部分序列的对比,发现全部个体在该片段上的序列完全一致,说明白暨豚遗传多样性极低。 相似文献
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94.
The study of heteromorphic Nostoc muscorum CALU 304 cells, whose formation was induced by 6- to 7-week cocultivation with the Rauwolfia callus tissues under unfavorable conditions, revealed the occurrence of giant cell forms (GCFs) with a volume which was 35–210 times greater than that of standard cyanobacterial cells. Some GCFs had an impaired structure of the murein layer of the cell wall, which resulted in a degree of impairment of the cell wall ranging from the mere loss of its rigidity to its profound degeneration with the retention of only small peptidoglycan fragments. An analysis of thin sections showed that all GCFs had enlarged nucleoids. The photosynthetic membranes of spheroplast-like GCFs formed vesicles with contents analogous to that of nucleoids (DNA strands and ribosomes). About 60% of the vesicles had a size exceeding 300 nm. With the degradation of GCFs, the vesicles appeared in the intercellular slimy matrix. It is suggested that the vesicles are analogous to elementary bodies, which are the minimal and likely primary reproductive elements of L-forms. The data obtained in this study indicate that such L-forms may be produced in the populations of the cyanobionts of natural and model syncyanoses. Along with the other known cyanobacterial forms induced by macrosymbionts, L-forms may represent specific adaptive cell forms generated in response to the action of plant symbionts. 相似文献
95.
Virulence in Candida species 总被引:7,自引:0,他引:7
Ken Haynes 《Trends in microbiology》2001,9(12):S437-596
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97.
J. O. A. Paucar R. M. S. Isaias J. R. Stehmann 《Plant biology (Stuttgart, Germany)》2020,22(2):146-156
- The tribe Schwenckieae (Solanaceae) is characterised by the presence of appendages on the corolla, a diagnostic trait for the group. These appendages constitute a median distal projection of the three‐lobed petal and occur in the genera Melananthus and Schwenckia but are absent in Heteranthia.
- We investigated the micromorphology and anatomical structure of the appendages and lateral petal lobes of Schwenckia americana (two varieties), S. angustifolia, S. curviflora and S. novaveneciana, and Melananthus fasciculatus. We also performed histochemical tests to determine if the appendages are involved in the production of volatiles, acting as a fragrance secretory structure (osmophore).
- The appendages have a uniseriate epidermis, whose cells store phenolics and lipids. The parenchyma is starch‐rich just prior to anthesis in all species studied. The sensory test and anatomical analyses identified scent‐secreting tissues, not only in the appendages, but also in the lateral petal lobes, whose cells are papillose with a sculptured surface. The α‐naphthol p‐phenylenediamine (NADI) reaction detected volatile (essential oils) compounds in S. americana var. americana and S. americana var. angustifolia.
- We demonstrated the secretory tissues and the production of lipids in the corolla appendages of Schwenckia and Melananthus, which indicate their osmogenic function and probable scent emission to attract pollinators.
98.
BackgroundKnowledge on Bi metabolism in laboratory animals refers to studies at “extreme” exposures, i.e. pharmacologically relevant high-doses (mg kg−1 b.w.) in relation to its medical use, or infinitesimal doses (pg kg−1b.w.) concerning radiobiology protection and radiotherapeutic purposes. There are no specific studies on metabolic patterns of environmental exposure doses (ultratrace level, μg kg−1 b.w.), becoming in this context Bi a “heavy metal fallen into oblivion”. We previously reported the results of the metabolic fate of ultratrace levels of Bi in the blood of rats [1]. In reference to the same study here we report the results of the retention and tissue binding of Bi with intracellular and molecular components.MethodsAnimals were intraperitoneally injected with 0.8 μg Bi kg−1 b.w. as 205+206Bi(NO)3, alone or in combination with 59Fe for the radiolabeling of iron proteins. The use of 205+206Bi radiotracer allowed the determination of Bi down to pg fg−1 in biological fluids, tissues, subcellular fractions, and biochemical components isolated by differential centrifugation, size exclusion chromatography, solvent extraction, precipitation, immunoprecipitation and dialysis.Main findingsAt 24 h post injection the kidney contained by far the highest Bi concentration (10 ng g−1 wt.w.) followed by the thymus, spleen, liver, thyroid, trachea, femur, lung, adrenal gland, stomach, duodenum and pancreas (0.1 to 1.3 ng g−1 wt.w.). Brain and testis showed smaller but consistently significant concentrations of the element (0.03 ng g−1 wt.w). Urine was the predominant route of excretion. Intracellularly, liver, kidney, spleen, testis, and brain cytosols displayed the highest percentages (35%–58%) of Bi of homogenates. Liver and testis nuclei were the organelles with the highest Bi content (24 % and 27 %). However, when the recovered Bi of the liver was recorded as percent of total recovered Bi divided by percent of total recovered protein the lysosomes showed the highest relative specific activity than in other fractions. In the brain subcellular fractions Bi was incorporated by neuro-structures with the protein and not lipidic fraction of the myelin retaining 18 % of Bi of the total homogenate. After the liver intra-subcellular fractionation: (i) 65 % of the nuclear Bi was associated with the protein fraction of the nuclear membranes and 35 % with the bulk chromatin bound to non-histone and DNA fractions; (ii) about 50 % of the mitochondrial Bi was associated with inner and outer membranes being the other half recovered in the intramitochondrial matrix; (iii) in microsomes Bi showed a high affinity (close to 90 %) for the membranous components (rough and smooth membranes); (iv) In the liver cytosol three pools of Bi-binding proteins (molecular size > 300 kDa, 70 kDa and 10 kDa) were observed with ferritin and metallothionein–like protein identified as Bi-binding biomolecules. Three similar protein pools were also observed in the kidney cytosol. However, the amount of Bi, calculated in percent of the total cytosolic Bi, were significantly different compared to the corresponding pools of the liver cytosol.ConclusionsAt the best of our knowledge the present paper represents the first in vivo study, on the basis of an environmental toxicology approach, aiming at describing retention and binding of Bi in the rat at tissue, intracellular and molecular levels. 相似文献
99.
100.
Hyperthermia is a process that uses heat from the spatial heat source to kill cancerous cells without damaging the surrounding healthy tissues. Efficacy of hyperthermia technique is related to achieve temperature at the infected cells during the treatment process. A mathematical model on heat transfer in multilayer tissues in finite domain is proposed to predict the control temperature profile at hyperthermia position. The treatment technique uses dual-phase-lag model of heat transfer in multilayer tissues with modified Gaussian distribution heat source subjected to the most generalized boundary condition and interface at the adjacent layers. The complete dual-phase-lag model of bioheat transfer is solved using finite element Legendre wavelet Galerkin approach. The present solution has been verified with exact solution in a specific case and provides a good accuracy. The effect of the variability of different parameters such as lagging times, external heat source, metabolic heat source and the most generalized boundary condition on temperature profile in multilayer tissues is analyzed and also discussed the effective approach of hyperthermia treatment. Furthermore, we studied the modified thermal damage model with regeneration of healthy tissues as well. For viewpoint of thermal damage, the least thermal damage has been observed in boundary condition of second kind. The article concludes with a discussion of better opportunities for future clinical application of hyperthermia treatment. 相似文献