Negative regulation of plastidial isoprenoid pathway by herbivore-induced ß-cyclocitral in Arabidopsis thaliana.

Insect damage to plants is known to up-regulate defense and down-regulate growth processes. While there are frequent reports about up-regulation of defense signaling and production of defense metabolites in response to herbivory, much less is understood about the mechanisms by which growth and carbon assimilation are down-regulated. Here we demonstrate that insect herbivory down-regulates the 2-C-methyl-D-erythritol-4-phosphate (MEP) pathway in Arabidopsis (Arabidopsis thaliana), a pathway making primarily metabolites for use in photosynthesis. Simulated feeding by the generalist herbivore Spodoptera littoralis suppressed flux through the MEP pathway and decreased steady-state levels of the intermediate 1-deoxy-D-xylulose 5-phosphate (DXP). Simulated herbivory also increased reactive oxygen species content which caused the conversion of ß-carotene to ß-cyclocitral (ßCC). This volatile oxidation product affected the MEP pathway by directly inhibiting DXP synthase (DXS), the rate-controlling enzyme of the MEP pathway in Arabidopsis and inducing plant resistance against S. littoralis ßCC inhibited both DXS transcript accumulation and DXS activity. Molecular models suggested that ßCC binds to DXS at the binding site for the thymine pyrophosphate cofactor and blocks catalysis, which was confirmed by direct assays of ßCC with the purified DXS protein in vitro. Another intermediate of the MEP pathway, 2-C-methyl-D-erythritol-2, 4-cyclodiphosphate, which is known to stimulate salicylate defense signaling, showed greater accumulation and enhanced export out of the plastid in response to simulated herbivory. Together, our work implicates ßCC as a signal of herbivore damage in Arabidopsis that increases defense and decreases flux through the MEP pathway, a pathway involved in growth and carbon assimilation.

Effect of modern infusion pumps on RBC quality.

BACKGROUND: Mechanical stress on red blood cells is associated with using infusion pumps for blood administration. Current standards in North America leave it to healthcare facilities to consult with manufacturers about infusion pump safety for transfusion; studies on various pumps and red blood cell (RBC) conditions are scarce. STUDY DESIGN AND METHODS: RBC units were pumped through four infusion pumps on d22 (22 days postcollection), d40, d28 after gamma irradiation on d14 (I14d28), and d22 after irradiation on d21 (I21d22). For each experiment, three units were pooled and split among four bags. Samples were collected at gravity and after pumping at clinical nonemergency rates. Hemolysis %, microvesicles, potassium, lactate dehydrogenase, mechanical fragility index levels, and morphology evaluations were performed (n = 5-6). RESULTS: Hemolysis levels of Piston and Linear Peristaltic pump samples were not different from hemolysis of corresponding gravity samples. Peristaltic samples had significantly higher hemolysis compared to gravity, and other pumps, however, maximum mean difference was limited to 0.05%. Pumping at 50 mL/h resulted in the highest hemolysis level. Change in hemolysis % due to pumping was significantly higher in d40 and I21d22 units. No combination of pumps and RBCs conditions led to hemolysis >0.8%. Besides hemolysis, lactate dehydrogenase release was the only marker that demonstrated some differences between infusions via pump versus gravity. CONCLUSION: The pump design affects the degree of hemolysis. However, for all tested pumps and RBC conditions, this increase was minimal. Hemolysis measurement on d40 and I21d22 at 50 mL/h were concluded to be appropriate parameters for pump evaluation.

Genome-Wide Identification of Wheat KNOX Gene Family and Functional Characterization of TaKNOX14-D in Plants.

The KNOX genes play important roles in maintaining SAM and regulating the development of plant leaves. However, the TaKNOX genes in wheat are still not well understood, especially their role in abiotic stress. In this study, a total of 36 KNOX genes were identified, and we demonstrated the function of the TaKNOX14-D gene under mechanical injury and cold stress. Thirty-six TaKNOX genes were divided into two groups, and thirty-four TaKNOX genes were predicted to be located in the nucleus by Cell-PLoc. These genes contained five tandem duplications. Fifteen collinear gene pairs were exhibited in wheat and rice, one collinear gene pair was exhibited in wheat and Arabidopsis. The phylogenetic tree and motif analysis suggested that the TaKNOX gene appeared before C3 and C4 diverged. Gene structure showed that the numbers of exons and introns in TaKNOX gene are different. Wheat TaKNOX genes showed different expression patterns during the wheat growth phase, with seven TaKNOX genes being highly expressed in the whole growth period. These seven genes were also highly expressed in most tissues, and also responded to most abiotic stress. Eleven TaKNOX genes were up-regulated in the tillering node during the leaf regeneration period after mechanical damage. When treating the wheat with different hormones, the expression patterns of TaKNOX were changed, and results showed that ABA promoted TaKNOX expression and seven TaKNOX genes were up-regulated under cytokinin and auxin treatment. Overexpression of the TaKNOX14-D gene in Arabidopsis could increase the leaf size, plant height and seed size. This gene overexpression in Arabidopsis also increased the compensatory growth capacity after mechanical damage. Overexpression lines also showed high resistance to cold stress. This study provides a better understanding of the TaKNOX genes.

A source-sink model explains the difference in the metabolic mechanism of mechanical damage to young and senescing leaves in Catharanthus roseus.

BACKGROUND: Mechanical damage is an unavoidable threat to the growth and survival of plants. Although a wound to senescing (lower) leaves improves plant vitality, a wound to younger (upper) leaves often causes damage to or death of the whole plant. Source-sink models are often used to explain how plants respond to biotic or abiotic stresses. In this study, a source-sink model was used to explain the difference in the metabolic mechanism of mechanical damage to young and senescing leaves of Catharanthus roseus. RESULTS: In our study, GC-MS and LC-QTOF-MS metabolomics techniques were used to explore the differences in source-sink allocation and metabolic regulation in different organs of Catharanthus roseus after mechanical damage to the upper/lower leaves (WUL/WLL). Compared with that of the control group, the energy supplies of the WUL and WLL groups were increased and delivered to the secondary metabolic pathway through the TCA cycle. The two treatment groups adopted different secondary metabolic response strategies. The WLL group increased the input to the defense response after damage by increasing the accumulation of phenolics. A source-sink model was applied to the defensive responses to local (damaged leaves) and systemic (whole plant) damage. In the WUL group, the number of sinks increased due to damage to young leaves, and the tolerance response was emphasized. CONCLUSION: The accumulation of primary and secondary metabolites was significantly different between the two mechanical damage treatments. Catharanthus roseus uses different trade-offs between tolerance (repair) and defense to respond to mechanical damage. Repairing damage and chemical defenses are thought to be more energetically expensive than growth development, confirming the trade-offs and allocation of resources seen in this source-sink model.

An auxin-mediated regulatory framework for wound-induced adventitious root formation in tomato shoot explants.

Adventitious roots (ARs) are produced from non-root tissues in response to different environmental signals, such as abiotic stresses, or after wounding, in a complex developmental process that requires hormonal crosstalk. Here, we characterized AR formation in young seedlings of Solanum lycopersicum cv. 'Micro-Tom' after whole root excision by means of physiological, genetic and molecular approaches. We found that a regulated basipetal auxin transport from the shoot and local auxin biosynthesis triggered by wounding are both required for the re-establishment of internal auxin gradients within the vasculature. This promotes cell proliferation at the distal cambium near the wound in well-defined positions of the basal hypocotyl and during a narrow developmental window. In addition, a pre-established pattern of differential auxin responses along the apical-basal axis of the hypocotyl and an as of yet unknown cell-autonomous inhibitory pathway contribute to the temporal and spatial patterning of the newly formed ARs on isolated hypocotyl explants. Our work provides an experimental outline for the dissection of wound-induced AR formation in tomato, a species that is suitable for molecular identification of gene regulatory networks via forward and reverse genetics approaches.

Mechanical sensitivity of red blood cells improves in individuals with hemochromatosis following venesection therapy.

BACKGROUND: Individuals with hereditary hemochromatosis (HH) receive frequent blood withdrawals (ie, venesections) as part of their primary treatment to assist in normalizing blood iron levels. It remains unclear whether this source of blood is suitable for use in blood product development, as current data indicate that red blood cell (RBC) deformability, both before and after shear stress exposure, is impaired in individuals with HH, relative to healthy controls. Given that venesection therapy is known to significantly reduce circulating iron levels in individuals with HH, the current study examined whether venesection therapy is effective at improving RBC mechanical properties, both before and after shear stress exposure, in individuals with HH. STUDY DESIGN AND METHODS: Blood samples were initially collected from untreated HH patients (age, 61 ± 9 years; 14% female) undergoing their first venesection, and then again during their second (approx. 9 weeks later) and third (approx. 16 weeks later) venesections. RBC deformability was measured at each time point with a commercial ektacytometer. Moreover, to determine cell responses to mechanical stimuli, the mechanical sensitivity of blood samples was determined at each time point. RESULTS: The salient findings indicate that venesection therapy used for managing plasma ferritin concentration significantly improves the cellular deformability of RBC in individuals with HH. Further, the sensitivity of RBC to supraphysiological mechanical stress is decreased (ie, improved) in a dose-response fashion with routine venesection. CONCLUSION: While cellular mechanics of RBC from individuals with HH are impaired when untreated, venesection therapy significantly improves cellular properties of RBC, supporting the use of venesections in blood product development from individuals with well-managed HH.

A mechanical approach to understanding the impact of the nematode Anguillicoloides crassus on the European eel swimbladder.

One of the most detrimental factors in the drastic decline of the critically endangered European eel (Anguilla anguilla) was the inadvertent introduction of the invasive nematode Anguillicoloides crassus Infection primarily affects the swimbladder, a gas-filled organ that enables the eel to control its depth in the water. A reduction in swimbladder function may be fatal for eel undergoing their spawning migration to the Sargasso Sea, a journey of over 5000 km. Although the physiological damage caused by this invasive parasite is well studied through the use of quantifiable gross pathological indices, providing a good measure of the swimbladder health status, they cannot separate the role of mechanical and morphological damage. Our study examined the appropriateness of three commonly used indices as a measure of mechanical damage by performing uniaxial tensile tests on swimbladder specimens obtained from an infected eel population. When the test results were compared with the gross pathological indices it was found that thickness correlated most strongly with mechanical damage, both confirming and, more importantly, explaining the counterintuitive findings of earlier work. In a damaged swimbladder, the immune response leads to a trade-off; increasing wall thickness raises the pressure required for organ rupture but decreases strength. The results indicate that for moderate infection the mechanical integrity of the swimbladder can be maintained. For severe infection, however, a reduction in mechanical integrity may reach a tipping point, thereby affecting the successful completion of their oceanic migration.

Postharvest benzothiazole treatment enhances healing in mechanically damaged sweet potato by activating the phenylpropanoid metabolism.

BACKGROUND: Sweet potato often suffers mechanical damage during harvest, handling, and transportation. Infections, water loss, and quality changes of sweet potato caused by mechanical damage pose great financial losses. Wound healing is an effective method to alleviate such problems. In this study, the effects of postharvest treatment with benzothiazole (BTH) on wound healing of sweet potato was investigated. RESULTS: Postharvest BTH treatment of sweet potatoes promoted lignin accumulation in wounded tissues, and 100 mg L-1 BTH exhibited better effects than 50 mg L-1 or 150 mg L-1 BTH. The biosynthesis of lignin in wounded tissues significantly decreased the weight loss of sweet potatoes. An increase in respiration intensity after BTH treatment was observed. The total phenolic and flavonoid contents and the activity of phenylalanine ammonia-lyase, peroxidase, and polyphenol oxidase were increased in BTH-treated sweet potatoes. This suggests that BTH increases phenylpropanoid metabolism. CONCLUSION: Postharvest 100 mg L-1 BTH treatment could promote wound healing in mechanically damaged sweet potatoes. The activation of the phenylpropanoid metabolism might be the mechanism of action of BTH in wound healing. © 2020 Society of Chemical Industry.

Specific Environmental Temperature and Relative Humidity Conditions and Grafting Affect the Persistence and Dissemination of Salmonella enterica subsp. enterica Serotype Typhimurium in Tomato Plant Tissues.

Little is known about the abiotic factors contributing to the preharvest persistence of Salmonella in tomato tissues. Therefore, we investigated the effects of specific environmental conditions and contamination methods on the persistence and dissemination of Salmonella enterica subsp. enterica serotype Typhimurium (JSG626) in tomato plants. When plants were sprayed on the leaves with a JSG626-contaminated solution, JSG626 persistence in the phyllosphere (bacteria located on the surface of the inoculated foliage and stem tissues) was lower at higher temperatures (30°C day/25°C night) than at lower temperatures (20°C day/15°C night). However, wounding cotyledons with contaminated tools improved JSG626 persistence and the internalization rate (2.27%) in planta compared to spray inoculation (0.004%). The systemic dissemination of JSG626 to other tissues increased when contaminated plants were grown under low relative humidity (<40%); however, JSG626 was only detected in the root systems at later sampling times (between 21 and 98 days postinoculation [dpi]). Further, after tomato scions were grafted onto rootstocks using contaminated cutting tools, dissemination of JSG626 was preferentially basipetal and occasionally acropetal in the plants, with higher persistence rates and loads of JSG626 in root systems compared to foliar tissues. JSG626 was detected in the grafting point and root systems up to 242 dpi; however, none of the fruits harvested from contaminated plants between 90 and 137 dpi were positive for JSG626. This study demonstrates that environmental temperature and relative humidity could be good indicators for estimating the persistence of Salmonella enterica in tomato plants. Further, root systems may represent a risk for long-term persistence of Salmonella enterica in tomato plants.IMPORTANCE Tomatoes are one of the most widely produced vegetables around the world; however, fresh tomatoes have been connected to multiple wide-scale salmonellosis outbreaks over the past decades. Salmonella is commonly found in the environment and can persist in hostile conditions for several weeks before being internalized into plant tissues, where it is protected from conventional sanitation methods. In addition to biotic factors (host, inoculum size, and phytobiome), abiotic factors (environmental conditions) may affect the persistence of Salmonella in crop production. This study demonstrates that specific environmental conditions, the inoculation method, and the inoculum density affect the persistence and dissemination of JSG626 in tomato plant tissues. Our findings enhance the understanding of interactions between Salmonella enterica and fresh produce and may lead to the development of novel management practices on farms.

Exogenous skeletal muscle satellite cells promote the repair of levator palpebrae superioris mechanical damage in rat.

AIM OF THE STUDY: Blepharoptosis is a drooping of the upper eyelid, usually due to dysfunction of the levator palpebrae superioris (LPS). Recently, skeletal muscle satellite cells (SSCs) have been reported to promote the repair of damaged skeletal muscle. This study aims to investigate the potential contribution of exogenous SSCs to the regeneration of mechanically damaged LPS. MATERIALS AND METHODS: Thirty-two rats were randomly divided into four groups, including control group, SSCs-treated group, SSCs-treated injury group and non-treated injury group. After rats in injury groups were artificially lacerated on both the left and right LPS, HBBS (Hank's Balanced Salt Solution) containing SSCs was injected into upper eyelid tissue. After 7 days, the LPS muscle tissues were excised. In addition, skeletal muscle cells (SMCs) and SSCs were cocultured for use as an in vitro model, and the protective effects of SSCs on cultured SMCs were also investigated. RESULTS: Histological staining revealed that exogenous SSCs repaired the damaged muscle fibers and attenuated the fibrosis of LPS, possibly due to the increased level of IGF-1. In contrast, the level of IL-1ß, IL-6, TGF-ß1 and Smad2/3 (phospho-T8) were significantly reduced in the SSCs-treated group. The in vitro model using coculture of skeletal muscle cells (SMCs) and SSCs also revealed an increased level of IGF-1 and reduced level of inflammatory factors, resulting in a better cell survival rate. CONCLUSIONS: This study found that exogenous SSCs can promote the repair of LPS mechanical damage and provides new insight into the development of novel therapeutic approaches for blepharoptosis.

Classification of Processing Damage in Sugar Beet (Beta vulgaris) Seeds by Multispectral Image Analysis.

The pericarp of monogerm sugar beet seed is rubbed off during processing in order to produce uniformly sized seeds ready for pelleting. This process can lead to mechanical damage, which may cause quality deterioration of the processed seeds. Identification of the mechanical damage and classification of the severity of the injury is important and currently time consuming, as visual inspections by trained analysts are used. This study aimed to find alternative seed quality assessment methods by evaluating a machine vision technique for the classification of five damage types in monogerm sugar beet seeds. Multispectral imaging (MSI) was employed using the VideometerLab3 instrument and instrument software. Statistical analysis of MSI-derived data produced a model, which had an average of 82% accuracy in classification of 200 seeds in the five damage classes. The first class contained seeds with the potential to produce good seedlings and the model was designed to put more limitations on seeds to be classified in this group. The classification accuracy of class one to five was 59, 100, 77, 77 and 89%, respectively. Based on the results we conclude that MSI-based classification of mechanical damage in sugar beet seeds is a potential tool for future seed quality assessment.

Sublethal mechanical trauma alters the electrochemical properties and increases aggregation of erythrocytes.

Circulation of blood depends, in part, on the ability of red blood cells (RBCs) to aggregate, disaggregate, and deform. The primary intrinsic disaggregating force of RBCs is derived from their electronegativity, which is largely determined by sialylated glycoproteins on the plasma membrane. Given supraphysiological shear exposure - even at levels below those which induce hemolysis - alters cell morphology, we hypothesized that exposure to supraphysiological and subhemolytic shear would cleave membrane-bound sialic acid, altering the electrochemical and physical properties of RBCs, and thus increase RBC aggregation. Isolated RBCs from healthy donors (n = 20) were suspended in polyvinylpyrrolidinone. Using a Poiseuille shearing system, RBC suspensions were exposed to 125 Pa for 1.5 s for three duty-cycles. Following the first and third shear duty-cycle, samples were assessed for: RBC aggregation; the ability of RBCs to aggregate independent of plasma ("aggregability"); disaggregation shear rate; membrane-bound sialic acid content, and; cell electrophoretic mobility. Initial shear exposure significantly increased RBC aggregation, aggregability, and the shear required for rouleaux dispersion. Sialic acid concentration significantly decreased on isolated RBC membranes ghosts, and increased in the supernatant following shear. Initial shear exposure decreased the electrophoretic mobility of RBCs, decreasing the electronegative charge from -15.78 ±â€¯0.31 to -7.55 ±â€¯0.21 mV. Three exposures to the shear duty-cycle did not further compound altered RBC measures. A single exposure to supraphysiological and subhemolytic shear significantly decreased the electrochemical charge of the RBC membrane, concurrently increasing cell aggregation/aggregability. The cascading implications of hyperaggregation appears to potentially explain the ischemia-associated complications commonly reported following mechanical circulatory support.

Oxidative Stress Increases Erythrocyte Sensitivity to Shear-Mediated Damage.

Patients receiving mechanical circulatory support often present with heightened inflammation and free radical production associated with pre-existing conditions in addition to that which is due to blood interactions with nonbiological surfaces. The aim of this experimental laboratory study was to assess the deformability of red blood cells (RBC) previously exposed to oxygen free radicals and determine the susceptibility of these cells to mechanical forces. In the present study, RBC from 15 healthy donors were washed and incubated for 60 min at 37°C with 50 µM phenazine methosulfate (PMS; an agent that generates superoxide within RBC). Incubated RBC and negative controls were assessed for their deformability and susceptibility to mechanical damage (using ektacytometry) prior to the application of shear stress, and also following exposure to 25 different shear conditions of varied magnitudes (shear stress 1, 4, 16, 32, 64 Pa) and durations (1, 4, 16, 32, 64 s). The salient findings demonstrate that incubation with PMS impaired important indices of RBC deformability indicating altered cell mechanics by ∼19% in all conditions (pre- and postexposure to shear stress). The typical trends in shear-mediated changes in RBC susceptibility to mechanical damage, following conditioning shear stresses, were maintained for PMS incubated and control conditions. We demonstrated that free radicals hinder the ability of RBC to deform; however, RBC retained their typical mechanical response to shear stress, albeit at a decreased level compared with control following exposure to PMS. Our findings also indicate that low shear exposure may decrease cell sensitivity to mechanical damage upon subsequent shear stress exposures. As patients receiving mechanical circulatory support have elevated exposure to free radicals (which limits RBC deformability), concomitant exposure to high shear environments needs to be minimized.

Application of Deep Learning Architectures for Accurate and Rapid Detection of Internal Mechanical Damage of Blueberry Using Hyperspectral Transmittance Data.

Deep learning has become a widely used powerful tool in many research fields, although not much so yet in agriculture technologies. In this work, two deep convolutional neural networks (CNN), viz. Residual Network (ResNet) and its improved version named ResNeXt, are used to detect internal mechanical damage of blueberries using hyperspectral transmittance data. The original structure and size of hypercubes are adapted for the deep CNN training. To ensure that the models are applicable to hypercube, we adjust the number of filters in the convolutional layers. Moreover, a total of 5 traditional machine learning algorithms, viz. Sequential Minimal Optimization (SMO), Linear Regression (LR), Random Forest (RF), Bagging and Multilayer Perceptron (MLP), are performed as the comparison experiments. In terms of model assessment, k-fold cross validation is used to indicate that the model performance does not vary with the different combination of dataset. In real-world application, selling damaged berries will lead to greater interest loss than discarding the sound ones. Thus, precision, recall, and F1-score are also used as the evaluation indicators alongside accuracy to quantify the false positive rate. The first three indicators are seldom used by investigators in the agricultural engineering domain. Furthermore, ROC curves and Precision-Recall curves are plotted to visualize the performance of classifiers. The fine-tuned ResNet/ResNeXt achieve average accuracy and F1-score of 0.8844/0.8784 and 0.8952/0.8905, respectively. Classifiers SMO/ LR/RF/Bagging/MLP obtain average accuracy and F1-score of 0.8082/0.7606/0.7314/0.7113/0.7827 and 0.8268/0.7796/0.7529/0.7339/0.7971, respectively. Two deep learning models achieve better classification performance than the traditional machine learning methods. Classification for each testing sample only takes 5.2 ms and 6.5 ms respectively for ResNet and ResNeXt, indicating that the deep learning framework has great potential for online fruit sorting. The results of this study demonstrate the potential of deep CNN application on analyzing the internal mechanical damage of fruit.

The Detailed Bactericidal Process of Ferric Oxide Nanoparticles on E. coli.

While nanoparticles exert bactericidal effects through the generation of reactive oxygen species (ROS), the processes of the internalization of and the direct physical damage caused by iron oxide nanoparticles are not completely clear. We hypothesize that direct physical or mechanical damage of the cell membrane and cytoplasmic integrity by nanoparticles is another major cause of bacterial death besides ROS. The aim of this study is to investigate the process of the internalization of iron oxide nanoparticles, and to evaluate the effect of direct physical or mechanical damage on bacterial cell growth and death. The results demonstrate that iron oxide nanoparticles not only inhibited E. coli cell growth, but also caused bacterial cell death. Iron oxide nanoparticles produced significantly elevated ROS levels in bacteria. Transmission electronic microscopy demonstrated that iron oxide nanoparticles were internalized into and condensed the cytoplasm. Strikingly, we observed that the internalized nanoparticles caused intracellular vacuole formation, instead of simply adsorbing thereon; and formed clusters on the bacterial surface and tore up the outer cell membrane to release cytoplasm. This is the first time that the exact process of the internalization of iron oxide nanoparticles has been observed. We speculate that the intracellular vacuole formation and direct physical or mechanical damage caused by the iron oxide nanoparticles caused the bactericidal effect, along with the effects of ROS.

Repetitive Supra-Physiological Shear Stress Impairs Red Blood Cell Deformability and Induces Hemolysis.

The supra-physiological shear stress that blood is exposed to while traversing mechanical circulatory assist devices affects the physical properties of red blood cells (RBCs), impairs RBC deformability, and may induce hemolysis. Previous studies exploring RBC damage following exposure to supra-physiological shear stress have employed durations exceeding clinical instrumentation, thus we explored changes in RBC deformability following exposure to shear stress below the reported "hemolytic threshold" using shear exposure durations per minute (i.e., duty-cycles) reflective of that employed by circulatory assist devices. Blood collected from 20 male donors, aged 18-38 years, was suspended in a viscous medium and exposed to an intermittent shear stress protocol of 1 s at 100 Pa, every 60 s for 60 duty-cycles. During the remaining 59 s/min, the cells were left at stasis until the subsequent duty-cycle commenced. At discrete time points (15/30/45/60 duty-cycles), an ektacytometer measured RBC deformability immediately after shear exposure at 100 Pa. Plasma-free hemoglobin, a measurement of hemolysis, was quantified via spectrophotometry. Supra-physiological shear stress impaired RBC properties, as indicated by: (1) decreased maximal elongation of RBCs at infinite shear stress following 15 duty-cycles (P <0.05); (2) increased real-time RBC deformability during application of the supra-physiological shear stress protocol (100 Pa) following exposure to 1 duty-cycle (F (1.891, 32.15) = 12.21, P = 0.0001); and (3) increased plasma-free hemoglobin following 60 duty-cycles (P < 0.01). The present study indicates that exposure of RBCs to short-term, repeated supra-physiological shear stress, impairs RBC deformability, with the extent of impairment exacerbated with each duty-cycle, and ultimately precipitates hemolysis.

Mechanical Models of Compression and Impact on Fresh Fruits.

Well-designed and well-operated postharvest mechanical handling processes are vital if fresh fruits are to enter markets with minimal damage. The susceptibility of fruit to quality loss during handling is largely determined by mechanical contact and damage. This article reviews current understanding concerning the effect of impact and other mechanical contacts on fruits. It also discusses the major mechanical models that represent the interaction between fruits or a fruit and a surface. In total, 25 mechanical models associated with compression and impact behaviors of fresh fruits, mainly characterizing such behavior between 2 deformable spherical bodies and between a deformable spherical body and a rigid plate are reviewed. Finally, possible future research directions are discussed. The main challenge in fruit handling is to recognize and prevent microscopic damage to fruits, especially internal tissue/cell damage and microcracks resulting from multiple/repetitive impacts and compressions.

Multiscale Biomechanics of Tomato Fruits: A Review.

Bruising and other mechanical damage to fruit caused by external forces during and postharvesting is manifested at the macroscale but is ultimately the result of failure of cells at the microscale. However, fruits have internal structures and cells from different tissue types react differently to application of an external force. Not much is known about the effects of such forces on single cells within tissues and one reason for this is the lack of multiscale models linking macro- (organ or whole fruit), meso- (tissue), and micro- (cell) mechanics. This review concerns tomato fruits specifically as this is an important crop and is an excellent exemplar of past and proposed research in this field. The first consideration is the multiscale anatomy of tomato fruits that provides the basis for mechanical modeling. The literature on experimental methods for studying multiscale mechanics of fruit is then reviewed, as are recent results from using those methods. Finally, future research directions are discussed, in particular the combination of work over all scales. It is clear that a bottom-up approach incorporating single-cell mechanics in finite element models of whole fruit assumed to have internal structures is a promising way forward for tomato fruits but further method developments may be needed for these and other fruits and vegetables, in particular recovery of representative single cells from tissues for mechanical characterization.

Assessing the effects of free fall conditions on damage to chickpea seeds: A comprehensive examination of seed deterioration.

Impact damage is the most destructive effect on the seeds during harvesting, handling, and storage, both on-farm and off-farm. The chickpea seeds' dicotyledonous characteristics and large mass and size make them susceptible to mechanical damage under impact loading. Tests were conducted to determine the extent of damage to chickpea seeds due to the impact caused by free fall. The extent of internal damage to the chickpea seeds was determined, which included the measurement of seed deterioration by the accelerated aging method (percentage loss in germination in the accelerated aging test) and the measurement of electrical conductivity. Three independent variables were used in the test, namely: (a) drop height (3, 6, 9, and 12 m), (b) impact surface (concrete, metal, plywood and seeds on seeds), and (c) seed moisture content (10%, 15%, 20%, and 25% w.b). The results showed that drop height, impact surface, and moisture content had significant effects (p < .01) on the loss in germination percentage and change in electrical conductivity of chickpea seeds. In terms of loss in germination, the highest damage to seeds occurred at the metal impact surface (41.96%) and the least at the seed on the seed (29.71%). The highest amount of electrical conductivity was related to the seeds dropped on the metal (36.09 µS cm-1 g-1) and the lowest was related to seed-on-seed contact (21.68 µS cm-1 g-1). By increasing the drop height from 3 to 12 m, the loss in germination and electrical conductivity of seeds increased from 27.74% to 48.08% and from 18.72 to 40.47 µS cm-1 g-1, respectively. Increasing the moisture content of chickpea seeds from 10 to 25% causes a decrease in the amount of damage to the seeds in terms of electrical conductivity (from 38.40 to 21.18 µS cm-1 g-1), but increases the damage in the form of a loss in the percentage germination in the accelerated aging test (from 29.22% to 42.88%). To reduce the impact damage to peas caused by free fall, the height of the fall should be limited to about 6 m, and they should be prevented from hitting hard and rough surfaces.

Evolution Pattern in Bruised Tissue of 'Red Delicious' Apple.

The study of apple damage mechanisms is key to improving post-harvest apple treatment techniques, and the evolution pattern of damaged tissue is fundamental to the study of apple damage mechanisms. In the study, 'Red Delicious' apples were used to explore the relationship between damage and time. A cell death zone was found in the pulp of the damaged tissue after the apple had been bruised. The tissue damage was centered in the cell death zone and developed laterally, with the width of the damage increasing with injury time. The extent of tissue damage in the core and pericarpal directions varied. About 60% of the damaged tissue developed in the core direction and 40% in the pericarpal direction, and the damage ratios in both directions remained consistent throughout the injury. The depth of damage and the rate of damage were influenced by the impact force size and the difference in the size of the damaged part of the apple, but the damage development pattern was independent of the impact force size and the difference in the damaged part. The maximum damage rate was reached at about 30 min, and the depth of damage was stabilized at about 72 min. By studying the evolution pattern of the damaged tissue of the bruised 'Red Delicious' apple, it provides the research idea and theoretical basis for enhancing the prediction accuracy and robustness of early stage damage in apples.