Differences In Cell Structure Research Articles

Effect of environmental water activity on microbial inactivation by intense pulsed light (IPL).

In this study, the effect of environmental aw on microbial inactivation by intense pulsed light (IPL) was investigated. Three different microorganisms (Gram-positive bacteria, Gram-negative bacteria, and yeast) were used as test organisms. The effect of environmental aw was assessed by irradiating each microbial suspension in sodium chloride solutions with different environmental aw levels (0.99-0.80). As the aw decreased, the aggregation of intracellular material of cell interior was changed and the cell number was increased. However, there was no significant difference in microbial reduction according to the aw after the 0.23-3.05J/cm2 of IPL treatment. It was confirmed that yeast had the highest resistance to IPL because of the differences in cell structure and cell wall components between yeast and bacteria. Additional research is needed to clearly understand the inactivation mechanism according to the type of microorganism by controlling aw using various solutes.

Foliar water uptake and its influencing factors differ between female and male Populus euphratica

In arid ecosystems, foliar water uptake (FWU) plays an important role in improving plant physiological performance. However, the structural and physiological response mechanism of FWU between male and female woody desert plants has not been reported. Using the dioecious desert woody plant Populus euphratica, the current study explored the structural and physiological response mechanism of male and female P. euphratica leaves to water absorption via an FWU capacity experiment based on leaf epidermal cell wall components and cell structure, osmotic adjustment, and oxidative metabolism indicators. The results showed that both male and female P. euphratica plants could absorb water through leaves. The per unit area of leaf water absorption (AFWU) and the leaf absorption speed (k) of female P. euphratica were higher than those of male P. euphratica, and the TFWU was approximately twice that of male P. euphratica. The leaf thickness (LT), palisade tissue thickness (TP) and the contents of cellulose and pectin of female were significantly larger than those of male P. euphratica. The contents of sucrose, glucose, soluble sugar, proline and peroxidase in female leaves were significantly higher than those in male leaves. Multivariate factor analysis showed that the AFWU of the leaves was strongly correlated with glucose, cellulose, TP, and catalase, and the k was strongly correlated with starch, pectin, LT, and malondialdehyde. The FWU capacity of female P. euphratica was stronger than that of male P. euphratica, which was caused by the difference in cell structure and osmotic regulatory substances. These results provide a new perspective for understanding the water utilization mechanism reproduction strategy of dioecious plants.

Sterilization of food packaging by UV-C irradiation: Is Aspergillus brasiliensis ATCC 16404 the best target microorganism for industrial bio-validations?

In food industries UV-C irradiation is used to achieve decontamination of some packaging devices, such as plastic caps or laminated foils, and of those smooth surfaces that can be directly irradiated. Since its effectiveness can be checked by microbial validation tests, some ascospore-forming molds (Aspergillus hiratsukae, Talaromyces bacillisporus, Aspergillus montevidensis, and Chaetomium globosum) were compared with one of the target microorganisms actually used in industrial bio-validations (Aspergillus brasiliensis ATCC 16404) to find the species most resistant to UV-C. Tests were carried out with an UV-C lamp (irradiance = 127 μW/cm2; emission peak = 253.7 nm) by inoculating HDPE caps with one or more layers of spores. Inactivation kinetics of each strain were studied and both the corresponding 1D-values and the number of Logarithmic Count Reductions (LCR) achieved were calculated. Our results showed the important role played by the type of inoculum (one or more layers) and by the differences in cell structure (thickness, presence of protective solutes, pigmentation, etc.) of the strains tested. With a single-layer inoculum, Chaetomium globosum showed the highest resistance to UV-C irradiation (1D-value = 100 s). With a multi-layer inoculum, Aspergillus brasiliensis ATCC 16404 was the most resistant fungus (1D-value = 188 s), even if it reached a number of logarithmic reductions that was higher than those of some ascospore-forming mycetes (Aspergillus montevidensis, Talaromyces bacillisporus) tested.

A Quantitative Multivariate Microscopic Analysis for Identifying Changes of Glioblastoma Cancer Cells due to Thermochemoradiation Therapy

Introduction: Although radiation is recognized as the most effective nonsurgical treatment, the outcomes and control rates are generally poor. However, a combination of radiation therapy with hyperthermia and chemotherapy can improve the efficacy of treatment. The aim was to explore the potential of morphological and gradient-based features on microscopic images in improving the identification accuracy of subtle differences in cell structure during different treatments. Materials and Methods: Fifty single-cell images were used for each group and treatment regimen. The groups were individually subjected to: 1) hyperthermia at 43°C; 2) temozolomide (TMZ) chemotherapy at 10% inhibitory concentration; 3) radiotherapy at 2Gy; 4) combination of TMZ chemotherapy and hyperthermia; 5) combination of radiotherapy and hyperthermia; 6) combination of TMZ chemotherapy and radiotherapy; and 7) combination of TMZ chemotherapy, radiotherapy, and hyperthermia. Morphological and gradient-based features were extracted from each cell. The area under the receiver operating characteristic curve (AUC) was calculated for each significant feature to evaluate the performance of cell change detection. Results: According to AUCs, gradient-based features showed superior performance to morphological features in identifying cell changes during all treatment regimens in all groups. In this regard, the AUC of the gradient-mean feature exceeded 0.599 for all groups. The ratio of maximum to minimum cell diameter was the best morphological feature, with an AUC above 0.588 for all groups. Conclusions: Quantitative analysis of features is a reliable indicator of damage, with the potential to characterize cell changes during treatment regimens.

Adherens junction engagement regulates functional patterning of the cardiac pacemaker cell lineage.

Cardiac pacemaker cells (CPCs) rhythmically initiate the electrical impulses that drive heart contraction. CPCs display the highest rate of spontaneous depolarization in the heart despite being subjected to inhibitory electrochemical conditions that should theoretically suppress their activity. While several models have been proposed to explain this apparent paradox, the actual molecular mechanisms that allow CPCs to overcome electrogenic barriers to their function remain poorly understood. Here, we have traced CPC development at single-cell resolution and uncovered a series of cytoarchitectural patterning events that are critical for proper pacemaking. Specifically, our data reveal that CPCs dynamically modulate adherens junction (AJ) engagement to control characteristics including surface area, volume, and gap junctional coupling. This allows CPCs to adopt a structural configuration that supports their overall excitability. Thus, our data have identified a direct role for local cellular mechanics in patterning critical morphological features that are necessary for CPC electrical activity.

Effect of the order of incorporation of cake ingredients on the formation of batter and the final properties: contribution of the addition of pea flour.

The investigation dealt with the effect of the replacement of a part of wheat flour by pea flour on the properties of batters and cakes. As the protein composition of pea flour differs from that of wheat, the effect of its incorporation on batter formation and cake properties was monitored throughout the different steps of cake processing. The incorporation of air, which influences the cell structure and density of the cake, was the subject of particular attention. Four orders of incorporation were first investigated to identify their effects on a standard recipe made with 100% wheat flour. Mixing first egg and sugar together allows introducing air, but most of it is lost after oil and flour introduction. Whatever the order of incorporation, the density of the batter ends around 1.1 ± 0.2g.cm-1. However, batter consistencies are significantly different and resulting cakes show different crumb structures. These results are discussed in terms of physicochemical mechanisms, and a schematic representation of the phenomena occurring at the different steps of mixing depending on the order of ingredient incorporation is proposed. When 20 and 40% of the wheat flour was replaced by pea flour using the two most energy-efficient orders of incorporation, more air was incorporated into the batter. However, the resulting cakes were denser, but surprisingly softer. Differences in cell structure explain this apparent contradiction.

Low-velocity impact indentation rate sensitivity of aluminium foams

In this work, closed cell aluminium foams of different densities and correspondingly different cell structures were evaluated to characterise their impact indentation rate sensitivity i.e. increased indentation resistance with an increase in drop velocity. Impact indentation tests were carried out using an instrumented INSTRON 9350 drop weight impact tester. Drop velocity was varied from 1.81 to 6.85 m/s with corresponding impact energy varying between 9–120 J. The dynamic transmitted force (DTF) was taken as the measure of resistance to impact indentation and found to have a strong dependency on drop velocity and foam density. The foams with less than 0.53 g/cc density showed noticeable rate sensitivity, while the foams of higher density were rate insensitive. The dependence of rate sensitivity on foam density under impact indentation was related to the differences in cell structure for the low and high-density foams and the consequent differences in the mechanics of deformation. A hypothesis was proposed wherein the plateau borders of the hexagonal shaped cells (as seen in 2D sections) of the low-density foams, which were statistically aligned with the direction of loading, were envisaged to undergo inertia-induced compression before bending resulting in the enhancement of DTF at higher drop velocities. On the other hand, in the high-density foams with their characteristic circular shaped cells (as seen in 2D sections), deformation was only by plateau border bending and the rate sensitivity was negligible. The densified cell zone developing beneath the indenter stabilised the constraining forces, leading to rate-independent DTF.

Differences in cellular damage induced by dielectric barrier discharge plasma between Salmonella Typhimurium and Staphylococcus aureus

Dielectric barrier discharge (DBD) plasma treatments are more effective against Gram negative bacteria than Gram-positive bacteria. Effects of DBD plasma were compared on Salmonella Typhimurium and Staphylococcus aureus cells. Physical cell membrane integrity and function, deoxyribonucleic acid (DNA) oxidation, and intracellular reactive oxygen species (ROS) were measured. The difference in physical damage caused by plasma on Gram-negative and Gram positive bacteria implied a difference in cellular damage pattern, which may be due to differences in cell structure and composition. Antimicrobial particles in plasma react directly with the outer membranes of Gram-negative bacteria and eventually kill them; however, ROS produced from plasma first penetrated the cell wall and membrane of Gram-positive bacteria before reacting with internal cellular components and killing the bacteria.

Multiple physiological response analyses aid the understanding of sensitivity variation between Microcystis aeruginosa and Chlorella sp. under paraquat exposures

BackgroundSensitivity differences to chemical pollutants in different phytoplankton species may potentially shape the community structure of phytoplankton. However, detailed information supporting the understanding of sensitivity variations between phytoplankton species is still limited.ResultsTo investigate sensitivity differences between the cyanobacterium Microcystis aeruginosa, and the green alga Chlorella sp. to paraquat, multiple physiological parameters were measured and compared through acute and chronic toxicity assays. Early photosynthetic responses during acute toxicity assays showed that paraquat affects Photosynthesis System II energy fluxes in M. aeruginosa within 3 h of exposure, but not in Chlorella sp. After 5 h of cumulative exposure, an EC50 based on the maximum quantum yield for primary photochemistry of 0.54 mg L−1 was achieved and remained more or less constant, while the EC50 values for Chlorella fluctuated around 44.76 ± 3.13 mg L−1 after 24 h of exposure. During chronic 96 h exposure to paraquat, differences in antioxidant enzyme activities, reactive oxygen species (ROS) levels, and ultrastructure were observed in both M. aeruginosa and Chlorella sp. An increase in the intracellular levels of ROS and the number of plasma membrane damaged cells was observed in M. aeruginosa in the 0.2, 0.5, and 1.0 mg L−1 treatments (p < 0.01), but not for Chlorella. In addition, at an exposure level of 1.0 mg L−1, extensive disruption of cell structure was observed in M. aeruginosa. Conversely, little disarrangement of organelle structure was found in Chlorella sp.ConclusionThese results confirm that paraquat is more toxic to M. aeruginosa than to Chlorella sp. The sensitivity differences between these two species (one a prokaryote and the other a eukaryote) to paraquat might be partially explained by the differences in cell structure (cell wall and photosynthetic structure), the enzymatic antioxidant system, and the physiological vulnerability. The multiple physiological endpoint analysis approach used in the current study provides more detailed information for understanding the mechanisms of sensitivity variation between these phytoplankton species.

Mechanism of Male Gender Bias in Neuroblastoma Cell Lines Exposed to Fragrances: A Link to Autism Spectrum Disorder

Mechanism of Male Gender Bias in Neuroblastoma Cell Lines Exposed to Fragrances: A Link to Autism Spectrum Disorder Autism Spectrum Disorder (ASD) is a set of complex developmental disorders whose etiology is debatable. Although the symptoms may vary from person to person, they include impairment or loss of speech, lack of empathy, and social interaction deficiency. The cases of ASD have continued to increase drastically each year, with the CDC estimating 1:68 children diagnosed, along with 4 to 5 times more prevalence in males. It is believed that ASD is caused by a combination of genetic and environmental factors, but recent studies suggest that exposure to environmental chemicals may play a critical role in its pathogenesis. Although there are no biomarkers for the disease, low levels of oxytocin and arginine vasopressin have been reported. These neuropeptides play a critical role in the development of male brains. Here we assessed the potential neurotoxic effects of everyday female fragrances in order to determine if there are morphological and immunological changes to neurons, which may suggest that they contribute to the development of ASD during gestation. In order to determine whether chemicals in fragrances have a neurotoxic effect on fetal brain development, eight cell lines derived from male and female neuroblastoma were used as an experimental model. After exposure of the cells to the particular fragrances, immunostaining was performed with oxytocin receptor antibodies to determine the up or down regulations of these receptors. Immunofluorescence showed that cells exposed to fragrances significantly reduced the percentage of OT receptor positive neurons in fetal male brain cell lines, but not the female cell lines. Separately, differences in cell structure between the cells treated with fragrances and the untreated control cells were detected using hematoxylin and eosin (H&E) staining. There were significant changes observed, such as axon elongation and thinning. These results suggest a correlation between low levels of OT and fragrance exposure, with a potential cause for ASD. Statistical analysis of the characteristics observed through H&E staining and immunocytochemistry quantitatively helped determine the effects of the fragrances on the migration, differentiation, and organization of fetal brain neurons. This may shed light on the pathogenesis of autism and male gender bias.

The effect of strain-hardening on the morphology and mechanical and dielectric properties of multi-layered PP foam/PP film

Polypropylene (PP) foams are important in various industrial applications due to their unique mechanical and electrical properties. However, fabrication of microcellular PP foams is still limited because of polymer's rheological properties. In this work, the influence of rheological properties and the layer confinement effect on the microcellular morphology of foam/film structure and the mechanical and dielectric properties were investigated. Two types of long chain branched polypropylenes (BPPs) were used and named as BPP1 and BPP2, respectively. Talc micro-particles were used as a nucleating agent for crystallization. In uniaxial extensional flow, both BPPs exhibited strong strain-hardening behavior with the Trouton ratios well above 3 at all extensional rates, regardless of the talc content; however, BPP2 exhibited more strain-hardening than BPP1. 16 and 32 layered foam/film structures were then fabricated with BPP2 and 32 layered foam/film was fabricated with BPP1. The lower strain-hardening of BPP1 caused cell collapse and showed very little evidence of film layers separating the foam layers, while the stronger strain-hardening of BPP2 resulted in stable cell layers near the surface of the sheet and a non-coalesced cell structure. Mechanical properties in compression showed large differences in compressive strain due to the difference in cell structures. Dielectric property measurement on biaxially oriented 32-layer BPP2 foam/film, the one that showed the best cell structure and mechanical properties, showed much higher apparent dielectric constant (6–7) and higher release and stored energy densities than those of neat biaxially oriented polypropylene films.

Influence of Pigment Extraction on Pb(II) Biosorption of &lt;i&gt;Cladophora&lt;/i&gt; and &lt;i&gt;Spirogyra&lt;/i&gt; Algae Powder

The Cladophora and Spirogyra genera are classified within the green algae division. Species belonging to these genera comprise large filamentous algae, possess significant biomass, and are found in freshwater around the world. These characteristics give Cladophora and Spirogyra high potential to be developed as biological materials. For this study, we harvested fresh Cladophora and Spirogyra and produced algae powder using two of conventional procedures: with pigment extraction and without pigment extraction. The resulting algae powders were subjected to Pb(II) biosorption, and the differences in biosorption rates were subsequently analyzed. Our study found the following: (i) significant differences in cell structure, cell wall thickness, the type and content of cell composition, and the quantity of epiphytes between Cladophora and Spirogyra. This variation influenced the functional groups within the resulting algae powders and their binding sites, which further led to different levels of Pb(II) adsorption. (ii) Glacial acetic acid, a compound commonly employed in pigment extraction procedures, affected the functional groups and the binding sites of the resulting algae powders. For Cladophora algae powder, Pb(II) biosorption was reduced by 16.6 %; whereas for Spirogyra algae powder, Pb(II) biosorption was reduced by 19.8 %. (iii) The pigment extraction procedure exerted the most significant influence on the carbonyl groups and hydroxyl groups in algae powder. (iv) The pigment extraction procedure is not suitable for the preparation of algae powders which will be used for metal ion biosorption.

Antibacterial mechanism and application of ε-polylysine conjugation with dextran.

e-Polylysine-dextran conjugate is a compound conjugated with e-polylysine (PL) and dextran through the Maillard reaction. The antimicrobial activity of PL-dextran conjugate was investigated using six Gram-positive and Gram-negative bacteria. The integrity of the cell membranes of the representative bacteria was determined by the amount of intracellular components released from the cells. It was found that the PL-dextran conjugate retained most of the original antimicrobial activity of PL. When treated with PL or the PL-dextran conjugate, the amount of releasing materials at absorbance of 260 nm quickly increased in both Gram-negative and positive bacteria, but the absorbance values were different due to the difference in cell structures. Furthermore, an outer membrane (OM) permeability assay was performed by fluorescent probe 1-N-phenylnaphthylamine (NPN). The results showed that PL or PL-dextran conjugate rapidly increased the NPN uptake. In addition, the preservative effect and the emulsifying properties of the PL-dextran conjugate were also observed when it is applied in coffee whitner. These findings indicate that the PL-dextran conjugate can be applied in the food processing industry.

Effect of pre-drying and par-frying conditions on the crispness of French fries

An experimental design was used to study the effect of pre-drying (to 10, 15 and 20% weight loss) and par-frying conditions (160, 170 and 180 °C) on the crispness of French fries. Par-frying time was adjusted with a software program to obtain equal moisture content and internal texture for all samples. Crispness was evaluated with a sensory panel. Furthermore, samples were analysed with a texture analyser and with confocal scanning laser microscopy (CSLM). Par-frying at 180 °C resulted in a crispier product than at 160 and 170 °C. Pre-drying to 20% weight loss lead to blisters and reduced crispness in comparison with pre-drying to 10 and 15% weight loss. Instrumental texture measurements showed a good correlation with sensory crispness. Large differences in cell structure, such as blisters, could be observed with CSLM. CSLM was useful to explain results from the instrumental and sensory texture evaluation.

Chitosan Derivatives Killed Bacteria by Disrupting the Outer and Inner Membrane

Six kinds of water-soluble chitosan were prepared by grafting aminofunctionality onto chitosan at the C-6 position, and their antimicrobial activities were investigated against three Gram-negative and three Gram-positive bacteria. Among the derivatives, dimethylaminoethyl-chitosan (DMAEC) has the highest potential to suppress the growth of bacteria. To elucidate detailed antimicrobial modes of action against bacteria, cell integrity, outer membrane (OM), and inner membrane (IM) permeabilization assays were investigated. When treated with DMAEC, the release of 260 nm absorbing materials quickly increased for both Escherichia coli and Staphylococcus aureus, but the absorbance value was different due to the difference in cell structures. In OM and IM permeabilization assays, DMAEC rapidly increased 1-N-phenylnaphthylamine uptake and the release of cytoplasmic beta-galactosidase via an increase in the permeability of OM and IM. Moreover, DMAEC90 prepared from 90% deacetylated chitosan had more activity than DMAEC50 prepared from 50% deacetylated chitosan, and these results revealed that the antimicrobial action of water-soluble chitosans was dependent on the degree of deacetylation and the substituted group.

Antimicrobial action of novel chitin derivative

Aminoethyl-chitin (AEC) was synthesized in an attempt to both increase solubility of chitin in water and biological activity. AEC was obtained by grafting 2-chloroethylamino hydrochloride onto chitin at C-6 position. The structure of AEC was elucidated FT-IR and 1H NMR spectroscopy, and its antimicrobial activity was investigated using three Gram-positive and Gram-negative bacteria. The integrity of the cell membranes of the representatives E. coli and S. aureus was investigated by determining the release of intracellular components of cells. When treated with AEC, release of 260 nm absorbing materials quickly increased both E. coli and S. aureus, but absorbance value was different due to the difference in cell structures. For detailed study, outer membrane (OM) and inner membrane (IM) permeabilization assay were performed using the fluorescent probe 1- N-phenylnaphthylamine (NPN) and the release of cytoplasmic β-galactosidase activity. The results showed that AEC rapidly increased NPN uptake and the release of cytoplasmic β-galactosidase via increasing the permeability of OM and IM. In addition, cytotoxic effect of AEC was assessed using human lung fibroblast (MRC-5) cell line, and AEC showed less toxic against MRC-5.

Cellular behavior in embryogenic and non-embryogenic sugar beet calluses

The present study discusses the results of cytological studies of two kinds of sugar beet callus, i.e., embryogenic and non-embryogenic tissues. The calluses were produced through culture of secondary leaves on Murashige and Skoog medium containing two hormone combinations. One week after transfer of calluses onto fresh medium, their cells were viewed using electron microscopy and an image analyzer. Observations showed that cells of the two callus types had considerable differences in cell structure and various organelles. Of note were the high amount of polyploidization, rough endoplasmic reticulum, polysome, poly-nucleolus, and incomplete cell wall together with abnormal partitioning in non-embryogenic cells, as compared to embryogenic cells. In contrast, vacuolation of cytoplasm, perfect cell wall and partitioning structure, and the high proportion of nucleus/cytoplasm area were recognized in embryogenic cells.

Interactions between dendrimer biocides and bacterial membranes

Dendrimer biocides have been shown to be more potent than their small molecule counterparts. In this study, several techniques were utilized to investigate the interactions between quaternary ammonium functionalized poly(propylene imine) dendrimers and bacterial membranes. Both Gram-positive and Gram-negative bacteria were tested. The techniques employed include UV–Vis spectroscopy, differential scanning calorimetry, and bioluminescence. When treated with dendrimer biocides, release of 260nm adsorbing materials from Escherichia coli strains quickly increased and reached a plateau afterwards, while release of 260nm absorbing materials from Staphylococcus aureus increased monotonically with the concentration due to the difference in cell structures. The different release behavior also correlates with the antimicrobial properties against these two types of bacteria. Bioluminescence experiments using bacteria containing stress-responsive bioluminescent reporter gene fusions provided information suggesting that damage to the cell membranes is the primary mechanism of the antimicrobial action for dendrimer biocides. High concentrations of calcium ions can limit the efficacy of the dendrimer biocides, although the tested concentration range is much higher than most practical applications. Differential scanning calorimetry studies showed at high concentrations that dendrimer biocides formed precipitates with phospholipid vesicles, suggesting a strong interaction with this model of bacterial membrane. These results provide insight about the antibacterial action of dendrimer biocides and establish the basis for their mode of action.

Aislamiento, Patrón de Fermentación de Carbohidratos y Caracterización Morfológica de Bacterias Celulolíticas del Rumen de Bovinos Alimentados con Heno de Raigrás en Colombia

&lt;p&gt;En el Centro Nacional de Investigaciones “Tibaitatá” de Corpoica, localizado en un ecosistema trópical a una altura de 2550 m.s.n.m, se adelantó un estudio para caracterizar la población de bacterias celulolíticas ruminales de bovinos. Cinco cepas de bacterias anaerobias celulolíticas fueron aisladas a partir del contenido ruminal de bovinos alimentados con heno de raigrás (Lolium multijlorum). Las pruebas bioquímicas, el patrón de fermentación de carbohidratos y la caracterización morfológica, incluyendo los estudios de microscopía electrónica de transmisión de la membrana celular y el glicocáliz, permitieron clasificar las cepas aisladas como: Fibrobacter succinogenes succinogenes (F31 y F32), Fibrobacter succinogenes elongata(F33), Ruminococcus albus (R38) y Ruminococcus flavefaciens (R39). La cepa de R. albus fermentó un mayor número de fuentes de carbono que la cepa de R. flavefaciens, pero ambas, fermentaron celobiosa, pectina y xilano. Ninguna de las dos subespecies de Fibrobacter aisladas fermentó pentosas. Las cepas de Fibrobacter presentaron morfologías de colonia en roll-tube de agar celobiosa, no repor­ tadas en la literatura. La apariencia, tamaño y distribución del glicocáliz en las células de las cepas del género Ruminococcus hicieron posible la diferenciación de sus dos espe­ cies R. albus y R. flavefaciens y la confirmación del status taxonómico de las otras cepas celulolíticas. Las cepas aisladas constituyen las primeras entradas al banco de germoplasma microbial de referencia para bovinos en Colombia. Actualmente se adelantan los estudios de actividad enzimática celulolítica de estas cepas.&lt;/p&gt;&lt;p&gt; &lt;/p&gt;&lt;p&gt; &lt;/p&gt;&lt;p&gt;&lt;strong&gt;Isolation, Carbohydrate Fermentation Pattern and Morphological Characterization of Rumen Cellulolytic Bacteria of Cattle Fed Raygrass Hay in Colombia&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;A Characterization study of rumen cellulolytic bacteria of cattle was conducted at the National Research Center "Tibaitatá" of Corpoica, located in a highland (2550 m.a.s.l) tropical ecosystem of Colombia. Five anaerobic strains of cellulolytic bacteria (F31, F32, F33, R38 and R39) were isolated from the rumen contents of cattle fed on raygrass (Lolium multiflorum) hay. Classification of the isolated rumen bacteria strains was accomplished by biochemical tests, carbohydrate fermentation patterns and morphological characterization, including transmission electron microscopy (TEM) of cell membrane and glycocalix. The isolated strains were: Fibrobacter succinogenes succinogenes (F31y F32), Fibrobacter succi nogenes elongata (F33), Ruminococcus albus (R38) and Ruminococcus flavefaciens (R39).&lt;/p&gt;&lt;p&gt;Ruminococcus albus fermented more carbohydrate sources than Ruminococcus flavefaciens, however, both species fermented cellobiose, pectin and xilan Fibrobacter isolates did not ferment pentose sugar s. Six different types of morphology of the colony, sorne of them not reported previously, were observed in Fibrobacter isolates growing on agar-containing roll­ tubes. Ruminococcus species were identified as R. albus and R. fla vefaciens by differences in cell structure, size and distribution of the glycocalix. Ultrastructural studies confirmed the taxonomic status of isolated bacteria species. Isolated bacteria are the first entries to the reference rumen germplasm bank of cattle in Colombia. Enzymatic assays are being conducted to measure cellulolytic activity of the isolated strains. &lt;/p&gt;

Influence of Composition and Processing History on the Cellular Morphology of the Foamed Olefinic Thermoplastic Elastomers

Abstract Foam extrusion of a series of dynamically vulcanized polypropylene (PP)/ethylene-propylene-diene terpolymer (EPDM) blends (commercially available Santoprene) by using chemical blowing agents have been studied. Results suggest that foaming occurs only within the thermoplastic phase and for each composition there exists a limiting density which controls the maximum volume expansion. This limiting density is controlled only by the composition and is independent of the blowing agent concentration, extrusion conditions, and the geometry. For the softest and the hardest blends, maximum volume expansion was found to be about 20 and 100%, respectively. Considerable differences in cell structure were also observed with change in the blend composition. As the rubber content increases, bubbles change their shapes from spherical to highly elongated channels where long axes are primarily along the extrusion direction. When the shapes of the bubbles are viewed by cutting the specimen, the bubbles were found to become highly irregular as the rubber content was increased. The fractal dimension of the perimeter profiles revealed that increases in rubber content give increases in the characteristic fractal dimension. Additionally, wide angle x-ray pole figure analysis, which gives an average orientation behavior of the material, indicates that low levels of preferential crystalline chain orientation develop in the extradates. This preferential orientation was found to vary from skin to core.