Outer Tissue Research Articles

Establishment of the Vertebrate Germ Layers.

The process of germ layer formation is a universal feature of animal development. The germ layers separate the cells that produce the internal organs and tissues from those that produce the nervous system and outer tissues. Their discovery in the early nineteenth century transformed embryology from a purely descriptive field into a rigorous scientific discipline, in which hypotheses could be tested by observation and experimentation. By systematically addressing the questions of how the germ layers are formed and how they generate overall body plan, scientists have made fundamental contributions to the fields of evolution, cell signaling, morphogenesis, and stem cell biology. At each step, this work was advanced by the development of innovative methods of observing cell behavior in vivo and in culture. Here, we take an historical approach to describe our current understanding of vertebrate germ layer formation as it relates to the long-standing questions of developmental biology. By comparing how germ layers form in distantly related vertebrate species, we find that highly conserved molecular pathways can be adapted to perform the same function in dramatically different embryonic environments.

Intra-population variability of ocean acidification impacts on the physiology of Baltic blue mussels (Mytilus edulis): integrating tissue and organism response.

Increased maintenance costs at cellular, and consequently organism level, are thought to be involved in shaping the sensitivity of marine calcifiers to ocean acidification (OA). Yet, knowledge of the capacity of marine calcifiers to undergo metabolic adaptation is sparse. In Kiel Fjord, blue mussels thrive despite periodically high seawater PCO2, making this population interesting for studying metabolic adaptation under OA. Consequently, we conducted a multi-generation experiment and compared physiological responses of F1 mussels from 'tolerant' and 'sensitive' families exposed to OA for 1year. Family classifications were based on larval survival; tolerant families settled at all PCO2 levels (700, 1120, 2400µatm) while sensitive families did not settle at the highest PCO2 (≥99.8% mortality). We found similar filtration rates between family types at the control and intermediate PCO2 level. However, at 2400µatm, filtration and metabolic scope of gill tissue decreased in tolerant families, indicating functional limitations at the tissue level. Routine metabolic rates (RMR) and summed tissue respiration (gill and outer mantle tissue) of tolerant families were increased at intermediate PCO2, indicating elevated cellular homeostatic costs in various tissues. By contrast, OA did not affect tissue and routine metabolism of sensitive families. However, tolerant mussels were characterised by lower RMR at control PCO2 than sensitive families, which had variable RMR. This might provide the energetic scope to cover increased energetic demands under OA, highlighting the importance of analysing intra-population variability. The mechanisms shaping such difference in RMR and scope, and thus species' adaptation potential, remain to be identified.

Dynamic regulation of auxin oxidase and conjugating enzymes AtDAO1 and GH3 modulates auxin homeostasis

The hormone auxin is a key regulator of plant growth and development, and great progress has been made understanding auxin transport and signaling. Here, we show that auxin metabolism and homeostasis are also regulated in a complex manner. The principal auxin degradation pathways in Arabidopsis include oxidation by Arabidopsis thaliana gene DIOXYGENASE FOR AUXIN OXIDATION 1/2 (AtDAO1/2) and conjugation by Gretchen Hagen3s (GH3s). Metabolic profiling of dao1-1 root tissues revealed a 50% decrease in the oxidation product 2-oxoindole-3-acetic acid (oxIAA) and increases in the conjugated forms indole-3-acetic acid aspartic acid (IAA-Asp) and indole-3-acetic acid glutamic acid (IAA-Glu) of 438- and 240-fold, respectively, whereas auxin remains close to the WT. By fitting parameter values to a mathematical model of these metabolic pathways, we show that, in addition to reduced oxidation, both auxin biosynthesis and conjugation are increased in dao1-1 Transcripts of AtDAO1 and GH3 genes increase in response to auxin over different timescales and concentration ranges. Including this regulation of AtDAO1 and GH3 in an extended model reveals that auxin oxidation is more important for auxin homoeostasis at lower hormone concentrations, whereas auxin conjugation is most significant at high auxin levels. Finally, embedding our homeostasis model in a multicellular simulation to assess the spatial effect of the dao1-1 mutant shows that auxin increases in outer root tissues in agreement with the dao1-1 mutant root hair phenotype. We conclude that auxin homeostasis is dependent on AtDAO1, acting in concert with GH3, to maintain auxin at optimal levels for plant growth and development.

An Assessment of the Remodeling of Bifurca-tions in Hazel (Corylus avellana L.) in Response to Bracing, Drilling, and Splitting

The ability of trees to remodel their woody structure after injury or strain to outer tissues greatly assists in their survival; however, this remodeling process is complex because it is influenced by many factors. The speed and extent of remodeling of branch junctions in trees around a mechanical flaw, such as included bark, will dictate to what extent and for how long the junction is mechanically weakened. In this study, 100 normally formed bifurcations in semi-mature hazel (Corylus avellana L.) were artificially modified by being rodbraced, drilled through the apex or split, and then left to grow in situ. Two further groups were identified as controls: 120 normally formed bifurcations and 70 bark-included bifurcations. After two to four years, these bifurcations were harvested and underwent tests of their bending strength. The bifurcations rigidly braced over three growing seasons developed adverse taper in their branches and had only 70.5% of the bending strength of the normally formed bifurcations. Bifurcations with the central 20% of the xylem drilled out of them were capable of recovering fully from this defect; in contrast, split bifurcations were found to be highly vulnerable to failure during wind-loading events. This study concludes that a bifurcation may be considered compromised in its bending strength if its apex is compromised, but that semi-mature bifurcations in hazel do exhibit a good ability to remodel after injury. The role of thigmomorphogenesis in this remodeling process is assessed with reference to the rod-braced specimens that suffered no significant mechanical perturbation at their apices.

Integrated biomonitoring of airborne pollutants over space and time using tree rings, bark, leaves and epiphytic lichens

The integrated use of tree rings and outer tissues, and lichens, was tested for monitoring how pollutant concentrations vary in space and over time nearby an incinerator in industrial area in Central Italy. Trace elements in thalli of lichen Xanthoria parietina and in leaves, bark, wood of Quercus pubescens, as well as carbon, oxygen and nitrogen isotope ratios in tree rings were analyzed. Some trace elements in the leaves differed significantly between the plots, though this was not the case in lichens and bark. The values of δ13C and δ18O showed the same trend in all plots, while the values of δ15N were higher in the distal plot. The results indicated that trace elements were intercepted and collected by tree bark and leaves, as well as lichens, at low concentrations, and that they hardly entered into tree xylem tissues during the growing season to be stored into the woody tissues. Indeed, the study did not highlight marked changes over time and space, in accumulation of airborne pollutants in the selected biomonitors, most probably due to the low levels of industrial development. Nevertheless, the analysis of tree ring cores in combination with bark and leaves, and lichens might potentially contribute to depict historic impacts of airborne pollutants at pronounced concentrations.

Physiological and physico-chemical changes in green papaya (Carica papaya L. ‘Kaek Noul’) shreds taken from the outer or inner mesocarp

ABSTRACTThis study compared physiological and physico-chemical changes in shreds of green papaya (Carica papaya L. ‘Kaek Noul’), taken from inner and outer mesocarp tissues, during storage at 7ºC for up to 8 d. Reductions in the flesh firmness of shreds, microstructure, colouration, dry matter content (DMC), and fresh weight (FW) loss, and in the rates of respiration, ethylene production, and enzyme activities were measured. The rapid loss of firmness of green papaya ‘Kaek Noul’ shreds taken from the inner mesocarp was attributed to the larger and more loosely arranged cells of the inner mesocarp compared to the smaller and compact cells of the outer mesocarp. Shreds taken from the outer mesocarp had a higher DMC [6.21–6.77% (w/w)] than those from the inner mesocarp [5.83–6.34% (w/w)] during storage at 7ºC. FW loss was higher for shreds from the inner mesocarp than from the outer mesocarp (0.89–1.12% vs. 0.39–1.00%, respectively). Colour values (h°) were lower at the end of storage for shreds from the inner mesocarp than shreds from the outer mesocarp (104.38° and 111.94°, respectively). Moreover, scanning electron micrographs of shreds from inner mesocarp and outer mesocarp tissues showed that the slower loss of firmness in shreds from the outer mesocarp could be attributed to having smaller and more compact cells, as well as to lower ethylene production by the outer mesocarp. However, this was not related to cellulase activity. This study indicated why processors prefer to use shreds from the outer mesocarp of green papaya.

Interaction between deglutition, tongue posture, and malocclusion: A comparison of intraoral compartment formation in subjects with neutral occlusion or different types of malocclusion.

To test the null hypothesis of no significant difference in terms of intraoral pressure curve characteristics assessed simultaneously at the subpalatal space (SPS) and the vestibular space (VS), during different oral postures, between four groups with either an Angle Class II/1 (II1), Angle Class II/2 (II2), anterior open bite (O) malocclusion, or a neutral occlusion control group (I). Intraoral pressure recordings were performed simultaneously in the VS and SPS of 69 consecutive subjects (nII1 = 15; nII2 = 17; nO = 17; nI = 20; mean age/standard deviation 18.43/6.60 years). Assessments included defined sections of open mouth posture (OMP, 30 seconds), anteriorly closed mouth condition (60 seconds), dynamics by a tongue-repositioning maneuver (TRM, 60 seconds), swallowing, and positive pressure generation (PP, 10 seconds). Interactions of malocclusion, compartment location, and posture on pressure curve characteristics were analyzed by Kruskal-Wallis and Mann-Whitney U-tests, adopting an α level of 5%. Globally significant group differences were detected at the VS (plateau duration and median peak heights during TRM; area under pressure curve [AUC] during PP) and SPS (AUC during TRM and PP). Subjects with anteriorly nonopen dental configurations (groups I and II2) were able to keep negative pressure levels at the VS for longer time periods during TRM, compared to groups O and II1. The null hypothesis was rejected for mean VS plateau durations and peak heights and for SPS AUC. Negative pressures at the VS may stabilize outer soft tissues passively and may explain the dental arch form shaping effect by mimic muscles.

Cannabis sativa: The Plant of the Thousand and One Molecules.

Cannabis sativa L. is an important herbaceous species originating from Central Asia, which has been used in folk medicine and as a source of textile fiber since the dawn of times. This fast-growing plant has recently seen a resurgence of interest because of its multi-purpose applications: it is indeed a treasure trove of phytochemicals and a rich source of both cellulosic and woody fibers. Equally highly interested in this plant are the pharmaceutical and construction sectors, since its metabolites show potent bioactivities on human health and its outer and inner stem tissues can be used to make bioplastics and concrete-like material, respectively. In this review, the rich spectrum of hemp phytochemicals is discussed by putting a special emphasis on molecules of industrial interest, including cannabinoids, terpenes and phenolic compounds, and their biosynthetic routes. Cannabinoids represent the most studied group of compounds, mainly due to their wide range of pharmaceutical effects in humans, including psychotropic activities. The therapeutic and commercial interests of some terpenes and phenolic compounds, and in particular stilbenoids and lignans, are also highlighted in view of the most recent literature data. Biotechnological avenues to enhance the production and bioactivity of hemp secondary metabolites are proposed by discussing the power of plant genetic engineering and tissue culture. In particular two systems are reviewed, i.e., cell suspension and hairy root cultures. Additionally, an entire section is devoted to hemp trichomes, in the light of their importance as phytochemical factories. Ultimately, prospects on the benefits linked to the use of the -omics technologies, such as metabolomics and transcriptomics to speed up the identification and the large-scale production of lead agents from bioengineered Cannabis cell culture, are presented.

Transcriptional Regulation of Auxin Metabolism and Ethylene Biosynthesis Activation During Apple (Malus × domestica) Fruit Maturation

Apple cultivars exhibit considerable variation in fruit maturation patterns that could influence at-harvest fruit firmness and postharvest storability. Based on the results from our previous transcriptome profiling of apple fruit maturation and well-documented auxin–ethylene crosstalk in other plant processes, the current experiment attempts to get insight into the potential crosstalk between auxin metabolism and ethylene biosynthesis during apple fruit maturation and ripening. Weekly apple fruit samples were collected to include the early maturation stages until 2 weeks after physiological maturity for both ‘Minneiska’ and ‘Scifresh’ cultivars. The expression patterns for genes with annotated functions of auxin transport, conjugation, biosynthesis, and responses were profiled by qRT-PCR along the apple fruit ripening processes and in different apple fruit tissues (seed, core, cortex, and peel). The expression profiles of both auxin metabolism and ethylene biosynthesis genes correlated with the apple fruit maturation process, but with different expression patterns and strength in each cultivar. Temporal and spatial gene expression patterns from seed to the outer fruit tissues corresponded with the center-outward ripening characteristics of apple fruit. It seems that timely reduction of biologically active auxin, in apple fruit cells of specific tissue, is critical for the activation of ethylene biosynthesis, even though auxin is needed for early fruit development. Our results suggest that the regulation of auxin transport and homeostasis may contribute to the time of activation of the ethylene biosynthesis pathway in maturing apple fruit and consequently influence the time of ripening for a specific cultivar.

Scaffold-Free Fabrication of Osteoinductive Cellular Constructs Using Mouse Gingiva-Derived Induced Pluripotent Stem Cells.

Three-dimensional (3D) cell constructs are expected to provide osteoinductive materials to develop cell-based therapies for bone regeneration. The proliferation and spontaneous aggregation capability of induced pluripotent stem cells (iPSCs) thus prompted us to fabricate a scaffold-free iPSC construct as a transplantation vehicle. Embryoid bodies of mouse gingival fibroblast-derived iPSCs (GF-iPSCs) were seeded in a cell chamber with a round-bottom well made of a thermoresponsive hydrogel. Collected ball-like cell constructs were cultured in osteogenic induction medium for 30 days with gentle shaking, resulting in significant upregulation of osteogenic marker genes. The constructs consisted of an inner region of unstructured cell mass and an outer osseous tissue region that was surrounded by osteoblast progenitor-like cells. The outer osseous tissue was robustly calcified with elemental calcium and phosphorous as well as hydroxyapatite. Subcutaneous transplantation of the GF-iPSC constructs into immunodeficient mice contributed to extensive ectopic bone formation surrounded by teratoma tissue. These results suggest that mouse GF-iPSCs could facilitate the fabrication of osteoinductive scaffold-free 3D cell constructs, in which the calcified regions and surrounding osteoblasts may function as scaffolds and drivers of osteoinduction, respectively. With incorporation of technologies to inhibit teratoma formation, this system could provide a promising strategy for bone regenerative therapies.

Impact of light-exposure on the metabolite balance of transgenic potato tubers with modified glycoalkaloid biosynthesis

Metabolite profiling (liquid chromatography–mass spectrometry (LC–MS) and gas chromatography (GC–MS)) was used to assess the impact of light on the composition of transgenic potato (Solanum tuberosum L. cv. Desirée) with reduced glycoalkaloid content via the down-regulation of the SGT1 gene. Transgenic tubers exhibited an almost complete knock-out of α-solanine production and light had little impact on its accumulation. Levels of α-chaconine increased significantly in the peel of both the control and transgenic lines when exposed to light, particularly in the transgenic line. Major differences in metabolite profiles existed between outer and inner tuber tissues, and between light and dark-treated tubers. Many of the light-induced changes are explicable in terms of pathways known to be affected by stress responses. The impact of transgenesis on profiles was much less than that of tissue type or light and most differences were explicable in terms of the modification to the glycoalkaloid pathway.

Age-related changes in the fracture resistance of male Fischer F344 rat bone

In addition to the loss in bone volume that occurs with age, there is a decline in material properties. To test new therapies or diagnostic tools that target such properties as material strength and toughness, a pre-clinical model of aging would be useful in which changes in bone are similar to those that occur with aging in humans. Toward that end, we hypothesized that similar to human bone, the estimated toughness and material strength of cortical bone at the apparent-level decreases with age in the male Fischer F344 rat. In addition, we tested whether the known decline in trabecular architecture in rats translated to an age-related decrease in vertebra (VB) strength and whether non-X-ray techniques could quantify tissue changes at micron and sub-micron length scales. Bones were harvested from 6-, 12-, and 24-month (mo.) old rats (n=12 per age). Despite a loss in trabecular bone with age, VB compressive strength was similar among the age groups. Similarly, whole-bone strength (peak force) in bending was maintained (femur) or increased (radius) with aging. There was though an age-related decrease in post-yield toughness (radius) and bending strength (femur). The ability to resist crack initiation was actually higher for the 12-mo. and 24-mo. than for 6-mo. rats (notch femur), but the estimated work to propagate the crack was less for the aged bone. For the femur diaphysis region, porosity increased while bound water decreased with age. For the radius diaphysis, there was an age-related increase in non-enzymatic and mature enzymatic collagen crosslinks. Raman spectroscopy analysis of embedded cross-sections of the tibia mid-shaft detected an increase in carbonate subsitution with advanced aging for both inner and outer tissue.

PREVALENCE AND ANTIBIOTIC RESISTANCE OF FOOD BORNE BACTERIAL CONTAMINATION IN SOME EGYPTIAN FOOD food

This study was undertaken to investigate the prevalence and antibiotic resistance of food borne bacterial contamination in some Egyptian food. Total viable bacteria and total coliform bacteria were isolated from different sources of food; carbohydrates (bread, flour and basbousa), vegetables (outer and inner tissues of potato and outer and inner tissues of cucumber) and proteins (minced meat, cheese and milk). The study resulted in maximum value of total viable bacteria found in outer tissue of potato 68X104±1.0, while the minimum value found in inner tissues of potato and cucumber. The study resulted in total coliform was maximum value in minced meat 6.4X103±0.3. Basbousa and inner tissue of potato and cucumber were free from coliforms. The ability of isolates to producing proteolytic enzymes was tested, we found that 326 isolate (63.92%) from all isolates had this ability, thus we selected most 2 potent proteolytic isolates. The two isolates were identified as Bacillus cereus and Escherichia coli. The identification confirmed by microlog 34.20 system and 16SrRNA for two isolates and the same result was founded. Sensitivity tested for the most potent proteolytic species to 12 of the most commonly used antibiotics in the Egyptian pharmacy. The results showed that all species were sensitive to most of antibiotics, except B. cereus which was strongly susceptible to azteronam and ceftazidim. The data showed that raw meat, cooked food products, and raw milk were most commonly contaminated with foodborne pathogens and many pathogens were resistant to different antibiotics. The study provided useful information for assessment of the possible risk posed to consumers, which has significant public health impact.

Characterising kiwifruit (Actinidia sp.) near skin cellular structures using optical coherence tomography

Pre-harvest growing conditions during the development of fruit have impacts on fruit quality at the time of harvest and during storage. These impacts may result in differences in the skin properties of the fruit and some sub-surface cellular structural changes, which have potential effects on postharvest fruit quality and storability. Optical coherence tomography (OCT) is a non-destructive imaging method that enables acquisition of three-dimensional (3D) images of sub-surface structures of semi-transparent and turbid objects. This technology is a potential tool to provide new information about the structural nature of horticulture products. This work used five commercial kiwifruit cultivars, ‘G3’, ‘G9’, ‘G14’, ‘Hort16A’ and ‘Hayward’, where ‘Hayward’ was also manipulated with different orchard management practices (crop load and girdling), to investigate the properties of the layers of structures immediately underneath the periderm. Fruit samples were harvested at commercial maturity and then 3D OCT images of the skins were captured prior to fruit quality assessment. An automated image processing protocol was established to enable visualisation and characterisation of larger near skin cellular structures in the outer parenchyma tissue. There was no obvious differentiation between the observed large cells and the stone cells that are present in Actinidia chinensis cultivars. Significant differences in the microstructures of the sub-surface cells were found amongst five commercial kiwifruit cultivars. In general ‘G3’, ‘G14’ and ‘Hayward’ had larger and greater numbers of large sub-surface cells than ‘G9’ and ‘Hort16A’. The volume fraction of large cells in the near skin tissue was lower for the yellow-fleshed cultivars (‘G3’, ‘G9’ and ‘Hort16A’) in comparison to the green-fleshed cultivars (‘G14’ and ‘Hayward’). Low crop load increased maximum large cell length. However, no other effects of crop load and girdling were observed on the microstructures of the large cells in ‘Hayward’. Overall, OCT was an efficient non-destructive technique that can be utilised to reveal the structures of skin and sub-surface cellular layers with high resolution. The developed image processing protocol was suitable for the processing of large data sets with acceptable accuracy. However, more work should be carried out to overcome image artefacts caused by surface lenticels and trichomes. Limitations caused by low penetration depth should also be improved to allow better representation of the whole fruit structure.

Microvascular vessel preparation: What are we really removing during adventitial stripping?

Although adventitial stripping has been routinely recommended and practiced during vessel preparation for microsurgical anastomoses, detailed descriptions vary regarding the adequate extent of such maneuver. We aimed to histologically clarify which components of the vessel are removed during adventitial stripping, using arterial samples harvested during microsurgical breast reconstruction. Thirteen deep inferior epigastric arteries, nine internal mammary arteries, and four thoracodorsal arteries were evaluated in each step of vessel preparation, which were (1) grossly as a vascular bundle, (2) before vessel preparation, and (3) after vessel preparation under the operative microscope. Histologic components of each sample were evaluated under light microscopy. The combined thickness of the intima and the media and the thickness of the adventitia were measured and compared. Two distinctive layers of connective tissue were observed outside the media before vessel preparation. Outer loose areolar tissue with coarse fibers was mostly removed during vessel preparation. However, the inner adventitial layer with dense, fine collagen fibers consistently remained after vessel preparation and ostensible adventitial stripping. The average thickness of this layer was comparable with that of the media. Although there was no definitive demarcation between the two differential connective tissue layers, a vasa vasorum layer was distinctly seen between the two layers. The tissue removed during standard microsurgical vessel preparation or vessel stripping is not the entire layer of the adventitia, and the inner adherent layer of adventitia with fine collagen fibers should be preserved and included in the microsuture with the intima and media during anastomosis.

The optical, absorptive and chlorophyll fluorescence properties of young stems of five woody species

To reveal the roles of stems in responding to the surrounding light environment, the optical properties of stem tissues of five woody species and their effect on bark, xylem and pith photosynthesis were investigated. Species-specific bark morphology and the distribution of pigments along the stem cross-section altered the radial conduction of light to a different degree, but in all investigated species light gradients within stems were markedly steep and visible light was largely depleted within the outer bark and cortex of the stems. Thereby, optical properties of the outer and inner bark resulted in an internal light environment, which is very different from outside according to intensity and spectral composition. Among species PAR-transmittance of outer bark or periderm varied in quantity between mean values of 8.5 and 42% and PAR-transmittance of total bark between 2.2 and 6.2%. The blue-band of the spectrum was totally absorbed by the outer and inner bark tissues. In the red-band total bark transmittance varied between 2 and 11%. Thus, blue light can only trigger photosynthetic electron transport in the cell layers of the cortex near the stem surface, whereas in the underlying cell layers of the xylem or pith the energy for photosynthesis can only be provided by longer wavelengths (green and particularly red light). In all species, the internal light gradient matched well with the chlorophyll fluorescence properties of the respective stem tissues. The maximum and effective quantum efficiencies of PSII clearly decreased from the cortex toward the innermost stem tissues (xylem, pith), which showed also a lower capability of photosynthetic electron transport of PSII. Our results indicate not only that light signals can enter the interior of stems and are modified in quantity and quality by its path through the stem. There is evidence to suggest that the light regime within stems has also profound effects on plastid differentiation and thus the photosynthetic properties of the respective stem tissues.

Synchrotron-based X-ray absorption near-edge spectroscopy imaging for laterally resolved speciation of selenium in fresh roots and leaves of wheat and rice.

Knowledge of the distribution of selenium (Se) species within plant tissues will assist in understanding the mechanisms of Se uptake and translocation, but in situ analysis of fresh and highly hydrated plant tissues is challenging. Using synchrotron-based fluorescence X-ray absorption near-edge spectroscopy (XANES) imaging to provide laterally resolved data, the speciation of Se in fresh roots and leaves of wheat (Triticum aestivum L.) and rice (Oryza sativa L.) supplied with 1 μM of either selenate or selenite was investigated. For plant roots exposed to selenate, the majority of the Se was efficiently converted to C-Se-C compounds (i.e. methylselenocysteine or selenomethionine) as selenate was transported radially through the root cylinder. Indeed, even in the rhizodermis which is exposed directly to the bulk solution, only 12-31% of the Se was present as uncomplexed selenate. The C-Se-C compounds were probably sequestered within the roots, whilst much of the remaining uncomplexed Se was translocated to the leaves-selenate accounting for 52-56% of the total Se in the leaves. In a similar manner, for plants exposed to selenite, the Se was efficiently converted to C-Se-C compounds within the roots, with only a small proportion of uncomplexed selenite observed within the outer root tissues. This resulted in a substantial decrease in translocation of Se from the roots to leaves of selenite-exposed plants. This study provides important information for understanding the mechanisms responsible for the uptake and subsequent transformation of Se in plants.

Surface, thermodynamic and biological activities of some synthesized Gemini quaternary ammonium salts based on polyethylene glycol

Quaternary ammonium salts are frequently used as antimicrobial agents that disrupt cell membrane through the binding of their ammonium cations to anionic sites in the outer tissue of bacteria. This article describes the synthesis of Gemini quaternary ammonium salts (G600Br, G1000Br and G1500Br). The chemical structures of synthesized Gemini quaternary ammonium salts were confirmed using FT-IR and 1HNMR spectra. The surface activity of the synthesized surfactants were determined from the surface and interfacial tension measurements. The surface parameter including: the critical micelle concentration (CMC), effectiveness (πcmc), efficiency (Pc20), maximum surface excess (Γmax) and minimum surface area (Amin), were calculated from the surface tension measurements, also, the foaming and emulsification power were measured. The thermodynamic parameters of micellization and adsorption showed their tendency towards adsorption at the interfaces and also micellization in the bulk of their solutions. Screening tests of the synthesized compounds showed that the compounds exhibit an effective antimicrobial activity on a variety of bacteria including Gram-positive bacteria (Bacillus subtilis and Micrococcus luteus), Gram-negative bacteria (Bordetella pertussis and Escherichia coli) and Fungi (Candida albicans and Aspergillus niger).

Dynamic observation of the biodegradation of lignocellulosic tissue under solid-state anaerobic conditions

The solid-state anaerobic digestion (SS-AD) of wheat straw was characterized under low inoculated batch tests during 244days. High levels of degradation of the cellulose (52%±1) and hemicelluloses (55%±2) were observed at the final stages and associated to a methane yield of 204±16NmLgTS−1. Ultrastructural observations, using transmission electronic microscopy, indicated that microorganisms degraded wheat straw from the central to the outer tissue (i.e. parenchyma to epidermis), depending on cell chemical, physical accessibility and the degree of lignification. Furthermore, major degradation of sclerenchyma secondary walls was observed. The bioaccessibility of lignocellulosic structures of wheat straw is mainly limited by the external waxy layer (cuticle), tertiary cell walls, high silica content and access to the cell lumen.

Potential contributions of intimal and plaque hypoxia to atherosclerosis.

Injury of arterial endothelium by abnormal shear stress and other insults induces migration and proliferation of vascular smooth muscle cells (VSMCs), which in turn leads to intimal thickening, hypoxia, and vasa vasorum angiogenesis. The resultant new blood vessels extend from the tunica media into the outer intima, allowing blood-borne oxidized low-density lipoprotein (oxLDL) particles to accumulate in outer intimal tissues by extravasation through local capillaries. In response to oxLDL accumulation, monocytes infiltrate into arterial wall tissues, where they differentiate into macrophages and subsequently evolve into foam cells by uptaking large quantities of oxLDL particles, the latter process being stimulated by hypoxia. Increased oxygen demand due to expanding macrophage and foam cell populations contributes to persistent hypoxia in plaque lesions, whereas hypoxia further promotes plaque growth by stimulating angiogenesis, monocyte infiltration, and oxLDL uptake into macrophages. Molecularly, the accumulation of hypoxia-inducible factor (HIF)-1α and the expression of its target genes mediate many of the hypoxia-induced processes during plaque initiation and growth. It is hoped that further understanding of the underlying mechanisms may lead to novel therapies for effective intervention of atherosclerosis.