Determinants of Microdamage in Elderly Human Vertebral Trabecular Bone

Previous studies have shown that microdamage accumulates in bone as a result of physiological loading and occurs naturally in human trabecular bone. The purpose of this study was to determine the factors associated with pre-existing microdamage in human vertebral trabecular bone, namely age, architecture, hardness, mineral and organic matrix. Trabecular bone cores were collected from human L2 vertebrae (n = 53) from donors 54–95 years of age (22 men and 30 women, 1 unknown) and previous cited parameters were evaluated. Collagen cross-link content (PYD, DPD, PEN and % of collagen) was measured on surrounding trabecular bone. We found that determinants of microdamage were mostly the age of donors, architecture, mineral characteristics and mature enzymatic cross-links. Moreover, linear microcracks were mostly associated with the bone matrix characteristics whereas diffuse damage was associated with architecture. We conclude that linear and diffuse types of microdamage seemed to have different determinants, with age being critical for both types.     

Comparative Mechanical Properties and Histology of Bone

Different bone tissues differ in their amounts of porosity,mineralization,reconstruction, and preferred orientation. Allthese have important effects on mechanical properties. Veryporous, cancellous bone is always weaker and morecompliant thancompact bone on a weight for weight basis, yet it occurs inplaceswhere its energyabsorbing ability, or its low density,is advantageous. Bonevaries considerably in its mineralization,and such variations have quite disproportionate effects on mechanicalproperties. These variations can be shown to be adaptive. Inparticular, there must always be a compromise between stiffnessandresistanceto fracture; these two properties run contrary to each other.The reason for secondary remodeling is an unresolved problem,though in a few places the role of such remodeling in changingthe grain of the bone is clearly mechanically adaptive. Themechanical properties of non-mammalian bone are obscure, andas the histology of such bone is often quite different fromthat of mammalian bone, we are no doubt in for some surpriseswhen the mechanical properties ofnonmammalian bone are discovered.     

Age-Dependent Changes in Geometry,Tissue Composition and Mechanical Properties of Fetal to Adult Cryopreserved Human Heart Valves

There is limited information about age-specific structural and functional properties of human heart valves, while this information is key to the development and evaluation of living valve replacements for pediatric and adolescent patients. Here, we present an extended data set of structure-function properties of cryopreserved human pulmonary and aortic heart valves, providing age-specific information for living valve replacements. Tissue composition, morphology, mechanical properties, and maturation of leaflets from 16 pairs of structurally unaffected aortic and pulmonary valves of human donors (fetal-53 years) were analyzed. Interestingly, no major differences were observed between the aortic and pulmonary valves. Valve annulus and leaflet dimensions increase throughout life. The typical three-layered leaflet structure is present before birth, but becomes more distinct with age. After birth, cell numbers decrease rapidly, while remaining cells obtain a quiescent phenotype and reside in the ventricularis and spongiosa. With age and maturation–but more pronounced in aortic valves–the matrix shows an increasing amount of collagen and collagen cross-links and a reduction in glycosaminoglycans. These matrix changes correlate with increasing leaflet stiffness with age. Our data provide a new and comprehensive overview of the changes of structure-function properties of fetal to adult human semilunar heart valves that can be used to evaluate and optimize future therapies, such as tissue engineering of heart valves. Changing hemodynamic conditions with age can explain initial changes in matrix composition and consequent mechanical properties, but cannot explain the ongoing changes in valve dimensions and matrix composition at older age.     

Tensile Mechanical Properties of Swine Cortical Mandibular Bone

Temporary orthodontic mini implants serve as anchorage devices in orthodontic treatments. Often, they are inserted in the jaw bones, between the roots of the teeth. The stability of the mini implants within the bone is one of the major factors affecting their success and, consequently, that of the orthodontic treatment. Bone mechanical properties are important for implant stability. The aim of this study was to determine the tensile properties of the alveolar and basal mandible bones in a swine model. The diametral compression test was employed to study the properties in two orthogonal directions: mesio-distal and occluso-gingival. Small cylindrical cortical bone specimens (2.6 mm diameter, 1.5 mm thickness) were obtained from 7 mandibles using a trephine drill. The sites included different locations (anterior and posterior) and aspects (buccal and lingual) for a total of 16 specimens from each mandible. The load-displacement curves were continuously monitored while loading half of the specimens in the oclluso-gingival direction and half in the mesio-distal direction. The stiffness was calculated from the linear portion of the curve. The mesio-distal direction was 31% stiffer than the occluso-gingival direction. The basal bone was 40% stiffer than the alveolar bone. The posterior zone was 46% stiffer than the anterior zone. The lingual aspect was stiffer than the buccal aspect. Although bone specimens do not behave as brittle materials, the diametral compression test can be adequately used for determining tensile behavior when only small bone specimens can be obtained. In conclusion, to obtain maximal orthodontic mini implant stability, the force components on the implants should be oriented mostly in the mesio-distal direction.     

Auxin- and Acid-Induced Changes in the Mechanical Properties of the Cell Wall

Auxin- and acid-induced changes in the mechanical propertiesof the cell wall were analyzed by measuring the creep of thecell wall using pumpkin (Cucurbita moschata Duch cv. Shirakikuza)hypocotyl segments. Hypocotyl segments were treated with orwithout IAA and stored in 50% glycerol at –15°C formore than 2 weeks before measurements. Creep rate increasedwith the increase in the load. The increase was first very slowup to the phase shift point (yield threshold, y), and afterthat, it was steep. The rate of the creep rate increase (creepcoefficient, Cm) was larger and y was smaller at pH 4.5 thanpH 6.8. This indicates cell wall loosening was facilitated underacidic conditions. IAA-pretreatment of the segments resultedin the lowering of y at pH 6.8 only. Around pH 5 and 45°C,Cm was highest and y was lowest. Boiling in distilled wateralmost lost the differential effect of Cm and y on pH and IAA.The differential effect of pH on Cm and y were recovered bythe addition of a crude extract of cell wall-bound proteins.It is implied that some enzymatic processes are involved inthe control of acid-induced cell wall extension. ¹Present address: Nihon Shokuhin Kako Co., Ltd. 30 Tajima, Fuji-City,Shizuoka, 417-8530 Japan. ²Present address: Graduate School of Environmental Earth Science,Hokkaido University, Sapporo, 060 Japan.     

Changes in the Biophysical Properties of Lymphocytes Under Mechanical Stress

Biophysics - Abstract—The biophysical properties of lymphocytes under mechanical deformations of blood cells were investigated. An in vitro model of mechanical “stress” helps to...     

Changes in Lipid Composition and Carbohydrate Composition of Aspergillus niger Conidia during Germination

Data on the lipid composition and carbohydrate composition of Aspergillus niger conidia make it possible to characterize the individual germination stages and differentiate between the conidia capable of germination and those that lost the germination capacity. The following criteria are proposed: the ratio of phosphatidylcholine and phosphatidylethanolamine, the ratio of mannitol and arabitol, and the levels of sterols and free fatty acids. The role of these compounds in the biochemical background of cell transition from dormancy to active metabolism and their use as indices of the quality of inocula in biotechnological processes are discussed.     

Microdamage Caused by Fatigue Loading in Human Cancellous Bone: Relationship to Reductions in Bone Biomechanical Performance

Vertebral fractures associated with osteoporosis are often the result of tissue damage accumulated over time. Microscopic tissue damage (microdamage) generated in vivo is believed to be a mechanically relevant aspect of bone quality that may contribute to fracture risk. Although the presence of microdamage in bone tissue has been documented, the relationship between loading, microdamage accumulation and mechanical failure is not well understood. The aim of the current study was to determine how microdamage accumulates in human vertebral cancellous bone subjected to cyclic fatigue loading. Cancellous bone cores (n = 32) from the third lumbar vertebra of 16 donors (10 male, 6 female, age 76±8.8, mean ± SD) were subjected to compressive cyclic loading at σ/E₀ = 0.0035 (where σ is stress and E₀ is the initial Young’s modulus). Cyclic loading was suspended before failure at one of seven different amounts of loading and specimens were stained for microdamage using lead uranyl acetate. Damage volume fraction (DV/BV) varied from 0.8±0.5% (no loading) to 3.4±2.1% (fatigue-loaded to complete failure) and was linearly related to the reductions in Young’s modulus caused by fatigue loading (r² = 0.60, p<0.01). The relationship between reductions in Young’s modulus and proportion of fatigue life was nonlinear and suggests that most microdamage generation occurs late in fatigue loading, during the tertiary phase. Our results indicate that human vertebral cancellous bone tissue with a DV/BV of 1.5% is expected to have, on average, a Young’s modulus 31% lower than the same tissue without microdamage and is able to withstand 92% fewer cycles before failure than the same tissue without microdamage. Hence, even small amounts of microscopic tissue damage in human vertebral cancellous bone may have large effects on subsequent biomechanical performance.     

Changes in Amino Acid Composition during Germination of Soybean

As a fundamental approach to the problem of amino acid metabolism in soybean, changes in content of twenty-three free amino acids, two acidic peptides, ammonia, ethanolamine, urea and seventeen total amino acids of cotyledon, hypocotyl and root of soybean during germination were determined with an amino acid analyzer. Glycine Max M. var. T201 (non-nodule-forming) and Glycine Max M. var. T202 (nodule-forming) were used for this experiment. The content and composition of free and total amino acids of cotyledon in both T201 and T202 differ from those of other tissues in any stage of germination. However, no significant difference between these two varieties of soybean has been recognized in patterns of free and total amino acids changes during germination.

In dry bean and initial stage of germination a relatively large unknown peak appeared and disappeared thereafter when the change in free amino acid content during germination of soybean was analyzed with amino acid analyzer. From various tests on the unknown peak, it became obvious that the peak was consisted of two peptides, γ-glutamyl-tyrosine and γ-glutamylphenylalanine, which were discovered in soybean by Thompson et al. in 1962. The content of these peptides did not change during the first 20 hours of germination, but they decreased rapidly thereafter and disappeared after 70 hours.     

Changes in Amino Acid Composition during Germination of Soybean

α- and γ-Glutamylaspartic acids were detected in acidic fraction of soybean seedling. R_F values of both peptides were consistent with those of authentic samples with several solvent systems.     

Changes in Amino Acid Composition during Germination of Soybean

Malonogalactan, a malonylated polysaccharide (—74° (c=1.6, H₂O)) produced by Penicillium citrinum, consisted of d-galactose and malonic acid in the approximate molar ratio of 3:1. Molecular weight of the demalonylated galactan (-99° (c=4.6, H₂O)) was about 40,000. From the data regarding optical rotation, nuclear magnetic resonance spectrum, infrared spectrum, glycosidase susceptibility, periodate oxidation, Smith degradation, methylation and acid hydrolysis, the possible structure of the Penicillium malonogalactan is deduced as follows: A galactan, 1,5-β-galactofuranoside polymer esterified with malonic acid at the position of 2 or 3.     

Changes in the Composition of the Essential Oil of Marjoram during Storage

The composition of volatile components of the essential oil of marjoram plants (Majorana hortensis M.) and its stability during storage were studied by capillary gas chromatography and gas chromatography/mass spectrometry. Storage in the dark for 1 year was associated with insignificant changes in the composition of the essential oil, and its organoleptic characteristics remained largely unaffected. Storage in the light produced considerable changes in the composition of the oil, due to chemical transformations of terpenoids.     

Nanoscale Examination of Microdamage in Sheep Cortical Bone Using Synchrotron Radiation Transmission X-Ray Microscopy

Microdamage occurs in bone through repeated and excessive loading. Accumulation of microdamage weakens bone, leading to a loss of strength, stiffness and energy dissipation in the tissue. Imaging techniques used to examine microdamage have typically been limited to the microscale. In the current study microdamage was examined at the nanoscale using transmission x-ray microscopy with an x-ray negative stain, lead-uranyl acetate. Microdamage was generated in notched and unnotched beams of sheep cortical bone (2×2×20 mm), with monotonic and fatigue loading. Bulk sections were removed from beams and stained with lead-uranyl acetate to identify microdamage. Samples were sectioned to 50 microns and imaged using transmission x-ray microscopy producing projection images of microdamage with nanoscale resolution. Staining indicated microdamage occurred in both the tensile and compressive regions. A comparison between monotonic and fatigue loading indicated a statistically significant greater amount of stain present in fatigue loaded sections. Microdamage occurred in three forms: staining to existing bone structures, cross hatch damage and a single crack extending from the notch tip. Comparison to microcomputed tomography demonstrated differences in damage morphology and total damage between the microscale and nanoscale. This method has future applications for understanding the underlying mechanisms for microdamage formation as well as three-dimensional nanoscale examination of microdamage.     

Mechanical Properties of Mesh Materials Used for Hernia Repair and Soft Tissue Augmentation

Background

Hernia repair is the most common surgical procedure in the world. Augmentation with synthetic meshes has gained importance in recent decades. Most of the published work about hernia meshes focuses on the surgical technique, outcome in terms of mortality and morbidity and the recurrence rate. Appropriate biomechanical and engineering terminology is frequently absent. Meshes are under continuous development but there is little knowledge in the public domain about their mechanical properties. In the presented experimental study we investigated the mechanical properties of several widely available meshes according to German Industrial Standards (DIN ISO).

Methodology/Principal Findings

Six different meshes were assessed considering longitudinal and transverse direction in a uni-axial tensile test. Based on the force/displacement curve, the maximum force, breaking strain, and stiffness were computed. According to the maximum force the values were assigned to the groups weak and strong to determine a base for comparison. We discovered differences in the maximum force (11.1±6.4 to 100.9±9.4 N/cm), stiffness (0.3±0.1 to 4.6±0.5 N/mm), and breaking strain (150±6% to 340±20%) considering the direction of tension.

Conclusions/Significance

The measured stiffness and breaking strength vary widely among available mesh materials for hernia repair, and most of the materials show significant anisotropy in their mechanical behavior. Considering the forces present in the abdominal wall, our results suggest that some meshes should be implanted in an appropriate orientation, and that information regarding the directionality of their mechanical properties should be provided by the manufacturers.     

Changes in the Composition of Volatile Compounds during Aging of Dry-cured Sausages

The change in the composition of volatile components during aging and storage of dry-cured sausages containing a mixture of Lactobacillus plantarumand Staphylococcus carnosusas fermenting cultures was studied by high-performance capillary gas chromatography and gas chromatography-mass spectrometry. A total of 52 compounds were identified. It was found that sausage storage is accompanied by a significant increase in the concentration of flavoring aldehydes. The terpene concentration monotonically increases with sausage aging and storage.     

Changes in Sterol Composition during Greening of Etiolated Barley Shoots

The following sterols were identified in barley shoots: stigmasterol, β-sitosterol, campesterol, and cholesterol. The total sterol content of green and etiolated tissue was 2.84 and 3.20 milligrams per gram dry weight, respectively. The free sterols accounted for most of the difference in total sterol content. The sterol ester, sterol glycoside, and acylated sterol glycoside contents of green and etiolated barley shoots were essentially the same. Etiolated tissue had twice as much total β-sitosterol as stigmasterol, while green tissue had equal amounts of these two sterols. The campesterol and cholesterol content was the same in green and etiolated tissue. This same sterol composition pattern held true for the free, glycosidic, and acylated glycosidic sterols; however, the sterol ester fraction had a completely different composition pattern. The esterified stigmasterol content was quite low in green and etiolated tissue, and campesterol was the second largest esterfied sterol component in etiolated tissue. Etiolated barley seedlings exposed to light had a shift in the ratio of free stigmasterol to β-sitosterol in favor of stigmasterol; however, no correlation was observed between chlorophyll synthesis and shift in sterol composition.     

Changes in the Lipid Composition of Thalassiosira pseudonana during Its Life Cycle

The lipid and fatty acid (FA) compositions of a marine diatom alga Thalassiosira pseudonana grown in culture were investigated. The relative content of separate lipid classes and their FA composition varied during of the life cycle. During the periods of active cell division and resting cell production, the proportion of polar lipids, as the structural components of cell membranes, increased. Changes in the proportion of lipid classes resulted in shifts in the FA composition of total lipids. It is suggested that the structural components of photosynthetic and cells membranes accumulate in the resting cells. Thereby, a rapid cell growth and an extensive development of the species under favorable environmental conditions is provided.