First Layer Of Cells Research Articles

Proteomic analysis of Morus leaf epidermis indicates the roles of photosystems and ROS in UV-B response

The epidermis is the first layer of cells on leaves that receive UV-B radiation and the place where guard cells distribute. Their stress response mechanism was different from the mesophyll. However, there has been little research on leaf epidermis. To assess the response mechanism of epidermis to UV-B radiation, tissue-specific proteomics were performed on the epidermis of Morus leaf under UV-B radiation and UV-B radiation following dark incubation. A total of 935 proteins were identified and quantified. Changes of proteins involved in light reaction and Calvin cycle were not simultaneous. Antioxidant enzymes showed different patterns. And the contents of H2O2 and Ca2+ were increased after treatments. A UV-B radiation response mechanism of epidermis was proposed based on these results, in which photosystems perceives the stimulus of UV-B radiation to produce reactive oxygen species, and then the antioxidant system and protein homeostasis system were induced through the Ca2+ crosstalk with reactive oxygen species signaling pathway.

Adaptive evolution at immune system genes and deep pregnancy implantation in primates

A major evolutionary change in the lineage ancestral to humans, chimpanzee and gorilla (HCG) has been the embedding of the embryo into maternal tissue. Thus, the first layer of cells (trophoblast) to differentiate after fertilization must adapt to invade the uterus. Such event would likely leave signatures of positive selection at genes with roles in embryo implantation. Here, 163 pregnancy implantation genes are tested for evidence of adaptive diversification in the ancestral lineage to HCG. Two immune system genes, HLA-E and KIR2DL4 showed evidence of positive selection. Some of the positive selected sites involve amino acid substitution with predicted damaging effects on protein function, thus highlighting the possibility of antagonistic pleiotropic effects. Selection at a gene coding for a receptor expressed in uterine cells (KIR) that interacts with trophoblast human leukocyte antigen (HLA) genes suggests a main role for immunological adaptations in embryo deep invasion of the maternal endometrium.

TRANSDUCTION OF STRAIN TO CELLS SEEDED ONTO SCAFFOLDS EXPOSED TO UNIAXIAL STRETCHING: A THREE DIMENSIONAL FINITE ELEMENT STUDY

When preparing tissue engineering and regenerative medicine constructs, a commonly encountered problem is the failure of seeded cells to infiltrate the scaffold. In an increasing number of cases, constructs are being mechanically preconditioned with the expectation that preconditioning will enhance the construct's maturation and effectiveness by pre-exposing seeded cells to stimuli the tissue of interest experiences in vivo. However, whether or not mechanostimulation of a scaffold actually results in transmission of stimuli to the seeded cells remains poorly understood. The purpose of this research was to develop a model that quantifies how strain is transmitted to cells layered on a scaffold's surface compared to cells embedded within a scaffold. Three-dimensional finite element models representative of these conditions were created. When 10% strain was applied to the construct, embedded cells received the full imposed strain. However, cells growing on top of the scaffold received 5% strain within the first layer of cells, and the strain transmitted to cells in subsequent layers decreased exponentially with increasing distance from the scaffold's surface. When experimentally testing the model, strain-induced biological responses were muted in conditions where cell to scaffold contact was reduced. This research illustrates the importance of achieving cellular penetration and cell-to-scaffold contacts when mechanically conditioning tissue engineering constructs.

Micro-PIXE investigation of bean seeds to assist micronutrient biofortification

This study compares the distribution and concentrations of micro- and macronutrients in different bean cultivars with the aim of optimizing the biofortification, a sustainable approach towards improving dietary quality. Micro-PIXE was used to reveal the distribution of Fe, Zn, Mn, Ca, P, S in seeds of common beans (Phaseolus vulgaris) and runner beans (Phaseolus coccineus). Average concentrations of elements in different tissues were obtained using ICP-AES. The highest concentrations of Zn in the studied beans were found in the embryonic axis, but an increased concentration of this element was also detected in the provascular bundles of the cotyledons. The first layer of cells surrounding provascular bundles accumulated high concentrations of Fe, while the next cell layer had an increased concentration of Mn. The analysis showed that the provascular bundles and the first cell layers surrounding them could have a significant role in the storage of important seed micronutrients – Zn, Fe, and Mn. This information has important implications for molecular biology studies aimed at seed biofortification.

Role of cell walls in the bioaccessibility of lipids in almond seeds

Certain nutrients and phytochemicals in almonds may confer protection against cardiovascular disease, but little is known about factors that influence their bioavailability. A crucial and relevant aspect is the amount of these dietary components available for absorption in the intestine, which is a concept referred to as bioaccessibility. We investigated the role played by cell walls in influencing the bioaccessibility of intracellular lipid from almond seeds. Quantitative analyses of nonstarch polysaccharides (NSPs) and phenolic compounds of cell walls were performed by gas-liquid chromatography and HPLC, respectively. In a series of experiments, the effects of mechanical disruption, chewing, and digestion on almond seed microstructure and intracellular lipid release were determined. In the digestibility study, fecal samples were collected from healthy subjects who had consumed diets with or without almonds. Almond seeds and fecal samples were examined by microscopy to identify cell walls and intracellular lipid. Cell walls were found to be rich in NSPs, particularly arabinose-rich polysaccharides, with a high concentration of phenolic compounds detected in the seed coat cell wall. During disruption of almond tissue by mechanical methods or chewing, only the first layer of cells at the fractured surface was ruptured and able to release lipid. In fecal samples collected from subjects consuming the almond diet, we observed intact cotyledonary cells, in which the cell walls encapsulated intracellular lipid. This lipid appeared susceptible to colonic fermentation once the cotyledonary cell walls were breached by bacterial degradation. The cell walls of almond seeds reduce lipid bioaccessibility by hindering the release of lipid available for digestion.

The origin of high hydraulic resistance for filter cakes of deformable particles: cell-bed deformation or surface-layer effect?

This study reports a numerical approach for modeling the hydraulic resistance of a filter cake of deformable cells. First, a mechanical and osmotic model that describes the volume fraction of solids in a bed of yeast cells as a function of the compressive pressure it experiences is presented. The effects of pressure on the compressibility of yeast cells beds were further investigated both by filtration experiments and by centrifugal experiments based on the multiple speed equilibrium sediment height technique. When comparing the latter measurements with compression model calculations, we observed that the method based on centrifugal experiments suffers from rapid relaxation of the compressed bed. Concerning the filtration experiments, specific resistance of well-defined bed of cells were calculated by a combination of the compression model with a formulation for hydraulic resistivity developed using the Lattice Boltzmann method. We further explain the experimental values observed for the hydraulic resistance of cell beds, assuming that the first layer of cells in contact with the membrane partially blocks the membrane area open to flow. In such a case, the blocked area seems to be a constant fraction of the normal cell–cell contact area.

Visualizing Superoxide Production in Normal and Diabetic Rat Islets of Langerhans

Oxygen free radicals have been implicated in beta-cell dysfunction and apoptosis associated with type 1 and type 2 diabetes mellitus. The roles of free radicals in diabetes have thus far been defined indirectly by monitoring oxidative tissue damage and the effects of antioxidants, free radical scavengers, and overexpression of superoxide dismutase. We employed the superoxide-mediated oxidation of hydroethidine to ethidium to dynamically and directly assess the relative rates of mitochondrial superoxide anion generation in isolated islets in response to glucose stimulation. Superoxide content of isolated islets increased in response to glucose stimulation. We next compared the oxyradical levels in Zucker lean control and Zucker diabetic fatty rat islets by digital imaging microfluorometry. The superoxide content of Zucker diabetic fatty islets was significantly higher than Zucker lean control islets under resting conditions, relatively insensitive to elevated glucose concentrations, and correlated temporally with a decrease in glucose-induced hyperpolarization of the mitochondrial membrane. Importantly, superoxide levels were elevated in islets from young, pre-diabetic Zucker diabetic fatty animals. Overproduction of superoxide was associated with perturbed mitochondrial morphology and may contribute to abnormal glucose signaling found in the Zucker diabetic fatty model of type 2 diabetes mellitus.

The Organotypic Multicellular Spheroid Is a Relevant Three-Dimensional Model to Study Adenovirus Replication and Penetration in Human Tumors in Vitro

The use of adenoviruses for gene transfer and as oncolytic agents is currently receiving widespread attention. As specific constraints to adenovirus distribution and spread cannot be studied in cell cultures, there is a need for an in vitro three-dimensional (3D) model mimicking the in vivo biology of tumors. We studied the interactions between tumor and adenoviruses using multicellular spheroids grown from primary brain tumor material. Using beta-galactosidase and luciferase reporter genes expressed by replication-defective adenoviruses, we showed that infection was restricted to the first layer of cells. Using a replication-competent adenovirus expressing the luciferase gene, we showed that transgene expression in the spheroid was considerably enhanced and that viral spreading deep into the 3D structure took place. In addition, a tetrazolium salt-based metabolic assay could be used to compare the oncolytic activity of different concentrations of replication-competent adenoviruses. We can conclude that organotypic spheroids offer a versatile in vitro system for studying distribution, spread, and oncolysis by adenoviruses in a clinically relevant model.

Transient variations of water transfer induced by HgCl2 in excised roots of young maize plants: new data on the inhibition process

Effects of low concentrations of HgCl2 on water transport in excised maize (Zea mays L.) roots have been monitored using a reliable system that permits continuous measurement of xylem flux variations. The sap flow of exuding roots treated with 11 M HgCl2 decreased by 80–90% in 10 min at 25˚C. Reversal of this inhibition was obtained using a sulfhydryl [β-mercaptoethanol (β-ME)], or non-sulfhydryl [ethylenediaminetetraacetate disodium salt (EDTA) and ferricyanide (FeCy)] reagents. The time course of reversal was not the same in the three cases. β-ME reversed quickly but not sustainably, whereas EDTA or FeCy reversed slowly and sustainably. Using a cell pressure probe, turgor was measured in the epidermis, and the first layer of cells in the cortex. Turgor was considerably decreased in root epidermal cells after HgCl2 treatment, suggesting that a normal root water-transfer required an optimal turgor in these cells. Recovery of cell turgor, was obtained satisfactorily with FeCy. In parallel with flux measurements, histochemical analyses revealed a localization of Hg only in peripheral root cells, suggesting that Hg targets are localized in the first root cell layers. Involvement of water channels and/or ion transport in the regulation of root water transport is discussed in the light of our data.

Differential deposition of suberin phenolic and aliphatic domains and their roles in resistance to infection during potato tuber (Solanum tuberosumL.) wound-healing

Rapid suberization of wounded potato tubers is critical in avoiding infection byErwinia carotovorasubsp.carotovora(a causal organism of bacterial soft rot) andFusarium sambucinum(a causal organism of fungal dry rot) in cut seed and stored potatoes. However, until now the reason for the differential development of resistance to bacterial and then fungal penetration during suberization has not been shown to be related to the differential deposition of the two major suberin components (phenolic and aliphatic domains) during wound-healing. Tubers of four varieties of diverse genetic background were wounded and inoculated withE. carotovorasubsp.carotovorathroughout a 5-day time course andF. sambucinumthroughout an 11-day time course during wound-healing (18 °C and 98% RH). During wound-healing, the tubers were examined at the cellular level for deposition of suberin phenolic and aliphatic domains. The percentage of inoculated tubers which became infected was determined for each wound-healing time point and was related to the deposition of suberin phenolic and aliphatic domains. Total resistance to infection byE. carotovorasubsp.carotovoraoccurred after the completion of phenolic deposition on the outer tangential wall of the first layer of cells (2–3 days). However, this suberin phenolic matrix offered no resistance to fungal infection byF. sambucinumeven after phenolic deposition was complete on adjoining radial and inner tangential cell walls of the first layer of cells. Resistance to fungal infection did not begin to develop until after deposition of the suberin aliphatic domain was initiated. Total resistance to fungal infection was attained after completion of deposition of the suberin aliphatic domain within the first layer of suberizing cells (5–7 days). These results indicate that the suberin phenolic domain provides resistance to infection byE. carotovorasubsp.carotovorabut not infection byF. sambucinum.They further suggest that deposition of the suberin aliphatic domain is responsible for final resistance to infection byF. sambucinum.This is believed to be the first evidence indicating separate depositional patterns, at the cellular level, for the two major domains of suberin and separate roles for each of these domains in the development of resistance to bacterial and fungal infection during suberization.

The separation and characterisation of haemocytes from the mussel Mytilus edulis

The separation of haemocytes from the mussel Mytilus edulis was carried out on continuous Percoll gradients. The haemocytes separated into three distinct layers, the first comprised 97% basophilic cells, the third comprised 84% eosinophilic cells and the middle layer was a mixture of eosinophilic and basophilic cells. Enzyme cytochemistry demonstrated arylsulphatase, phenol oxidase and peroxidase associated with the haemocytes from the third layer. Lectin-binding studies showed differential binding of lectins to the separated cells. The ultrastructural morphology demonstrated that the first layer of cells was composed predominantly of small agranular cells with a high nucleus to cytoplasm ratio. The second layer comprised a mixture of cells with the majority being granular cells with small granules. The third layer was almost exclusively composed of granular cells with small and large granules. Assays to assess the function of the different cells demonstrated that respiratory burst activity, measured as the reduction of cytochrome-c, was carried out almost entirely by the eosinophilic haemocytes. Similarly, levels of phagocytosis, measured as uptake of Escherichia coli, were much higher in the eosinophilic haemocytes. Of the potential mitogenic factors investigated, concanavalin A and pokeweed mitogen showed some evidence of inducing haemocyte proliferation.

Wound-Induced Tyramine Hydroxycinnamoyl Transferase in Potato ( Solanum tuberosum) Tuber discs

Summary The enzyme tyramine hydroxycinnamoyl transferase (THT) was induced by wounding in potato tuber discs ( Solanum tuberosum var. Bintje ). THT activity was barely detectable in the intact tuber but increased dramatically during two days in the outermost cell layers of the excised discs. Thereafter the activity declined but the enzyme remained induced for at least one week. The induction of THT, which was detectable 3 to 4 hours after wounding, was completely blocked by cycloheximide. The main products formed in vivo were identified as amides of ferulic acid with tyramine or octopamine. The concentration of these amides increased upon wounding but only about 6 days after preparation of the tuber slices. Mild alkaline hydrolysis of the suberin-enriched cell wall residue purified from healed tuber discs released feruloyltyramine and feruloyloctopamine together with free tyramine and octopamine. Moreover exogenously supplied [ 14 C]-feruloyltyramine was very rapidly integrated into the cell walls of the first layer of cells at the surface of wound healing tuber discs. Taken together our results suggest that the induction of THT and the integration of cinnamoyltyramines into cell walls could be part of the primary response of potato tuber tissues to wounding.

Detection of plasma cell immunoglobulins in tissue sections optimally fixed for ultrastructural immunocytochemistry.

We describe the ultrastructural localization of plasma cell immunoglobulins in vibratome sections of popliteal lymph nodes. Fixation with glutaraldehyde-paraformaldehyde gave better tissue and antigen preservation than paraformaldehyde or periodic acid lysine-paraformaldehyde; biotinylated Fab fragments of sheep anti-mouse IgG-streptavidin-biotinylated horseradish peroxidase (HRP) or Fab-HRP conjugates gave similar results. With both immunoreagents, excellent tissue preservation and antigen detection was observed in the first layer of cells sectioned with the vibratome. Conjugates of anti-mouse IgG with HRP did not show any staining. Peroxidase stain was observed in the nuclear envelope, cisternae of the rough endoplasmic reticulum, and the Golgi apparatus complex. In the Golgi apparatus, staining was seen consistently in cisternae of the cis face and in adjacent vesicles; the trans cisternae showed weak or no stain, and adjacent vesicles, "coated" vesicles, and granules were not stained. This study shows that high quality of tissue preservation and antigen detection, by both light and ultrastructural immunocytochemistry, is feasible in tissue fixed with glutaraldehyde-paraformaldehyde followed by vibratome sectioning and immunostaining with Fab-biotin-streptavidin-biotin-HRP, or Fab-HRP.