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PubMed2006

Protective effects of Peganum harmala L. extract, harmine and harmaline against human low-density lipoprotein oxidation.

Oxidative modification of low-density lipoprotein (LDL) particles has been implicated in the process of atherogenesis. Antioxidants that prevent LDL from oxidation may reduce atherosclerosis. We have investigated the protective effect of Peganum harmala-extract (P-extract) and the two major alkaloids (harmine and harmaline) from the seeds of P. harmala against CuSO4-induced LDL oxidation. Through determination of the formation of malondialdehyde (MDA) and conjugated diene as well as the lag phase, the extract (P-extract) and compounds were found to possess an inhibitory effect. Moreover, harmaline and harmine reduced the rate of vitamin E disappearance and exhibited a significant free radical scavenging capacity (DPPH*). However, harmaline had a markedly higher antioxidant capacity than harmine in scavenging or preventive capacity against free radicals as well as inhibiting the aggregation of the LDL protein moiety (apolipoprotein B) induced by oxidation. The results suggested that P. harmala compounds could be a major source of compounds that inhibit LDL oxidative modification induced by copper.

Adult↗
PubMed2005

Biotin-streptavidin-induced aggregation of gold nanorods: tuning rod-rod orientation.

We report herein biotin-streptavidin-mediated aggregation studies of long gold nanorods. We have previously demonstrated end-to-end linkages of gold nanorods driven by the biotin-streptavidin interaction (Caswell et al. J. Am. Chem. Soc. 2003, 125, 13914). In that report, the specific binding of biotin disulfide to the gold nanorod edges was achieved due to the preferred binding of thiol molecules to the Au[111] surface (gold nanorod ends) as opposed to the gold nanorod side faces. This led to the end-end linkage of gold nanorods upon subsequent addition of streptavidin. In this report we demonstrate a simple procedure to biotinylate the entire gold nanorod surface and subsequently form a 3-D assembly by addition of streptavidin. Gold nanorods were synthesized by the three-step seeding protocol documented in our previous articles. The surface of gold nanorods was further modified by a layer of a weak polyelectrolyte, poly(acrylic acid), PAA. A biotin molecule which has an amine group at one end (biotin-PEO-amine) was anchored to the carboxylic acid group of the polyelectrolyte using the well-known carbodiimide chemistry. This process biotinylates the entire gold nanorod surface. Addition of streptavidin further leads to aggregation of gold nanorods. A closer look at the aggregates reveals a preferential side-to-side assembly of gold nanorods. The gold nanorods were characterized at each stage by UV-vis spectroscopy, light scattering, and transmission electron microscopy (TEM) measurements.

Biotin↗
PubMed2005

The shield-backed bug, Pachycoris stallii: description of immature stages, effect of maternal care on nymphs, and notes on life history.

The life history of the shield-backed bug, Pachycoris stallii Uhler (Heteroptera: Scutelleridae), immatures was studied on its host plant, Croton californicus Muell.-Arg. (Euphorbiaceae), in Baja California Sur, Mexico. Immature stages are described and illustrated. Pachycoris stallii is bi- or multivoltine and occurs in xeric areas with sandy soil where it is rarely encountered away from C. californicus. Nymphs and adults feed on seeds within C. californicus fruit. Bugs oviposit on the underside of leaves, and females guard their eggs and first-instar nymphs from natural enemies. Embryonic orientation of prolarvae is nonrandom; each embryo is oriented with its venter directed toward the ground. This orientation may facilitate aggregation of first instars. The longitudinal axes of eggs are always oriented upward at about a 16 degree angle of deviation from a line perpendicular to the leaf surface. This is the first recorded observation of this phenomenon in Pentatomoidea. Experimental removal of females guarding first instars results in 100% loss of nymphs, and this is attributed to disruption of the aggregative behavior of nymphs. Maternal guarding appears to be a net benefit to P. stallii, despite possible costs to the brooding female.

Animals↗
PubMed1981

Epithelial organization and hormone sensitivity of toad urinary bladder cells in culture.

Two continuous cell lines (TB-M and TB-6c) derived from epithelial cells of the toad urinary bladder form epithelia in culture that manifest hormone-sensitive transepithelial transport. Development of transepithelial electrical resistance (R) and transport rate (ISC) are dependent on time and density of cells seeded, but steady-state ISC and R are characteristic for each cell line and independent of seeding density. Some responses of intact toad bladder are preserved in culture, whereas others are altered or absent. Neither cell line responds to vasopressin. Analogues of cAMP increase sodium transport and urea permeability in both cell lines but do not affect water permeability. The intramembrane particle aggregates associated with the vasopressin- and cAMP-induced increase in water permeability of the intact bladder could not be detected in the cell lines. Aldosterone increases sodium transport in both cell lines, and the time course and concentration dependence of the response to aldosterone are similar to those of the intact bladder. The relative effect of a series of steroids on ISC reveals corticosterone to be a more potent mineralocorticoid in cultured cells than in the intact bladder.

Animals↗
PubMed1991

Studies on the N-terminal sequences of lectins isolated from the seeds of Butea frondosa.

Two lectin fractions (FI and FII) were obtained from seeds of Butea frondosa by affinity chromatography on a sorbent of macroporous glass coupled to the disaccharide alpha-D-GalNAc-(1----3)-beta-D-Gal. Both of these fractions, although different in their sugar specificity, were found on SDS-PAGE to consist of two polypeptide chains of 33 kDa and 35 kDa. In the native state the subunits associated to form a 250 kDa complex, possibly comprising four molecules of the 33 kDa polypeptide and four molecules of the 35 kDa polypeptide. The presence of a faint 70 kDa band when the 250 kDa complex was subjected to SDS-PAGE may indicate the existence of a sequential mechanism of aggregation. N-terminal amino acid sequence analysis revealed extensive homology between these lectins and those of other Leguminosae.

Amino Acid Sequence↗
PubMed1987

Facilitation of actin polymerization by interfilamentous factors.

The polymerization of actin in low ionic strength buffer at 0 degrees C in the presence of 0.25 mM Mg2+ was studied by viscometry, turbidity and absorbance at 232 nm. Under these conditions, significant polymerization occurred only in the viscometer and not in isotropic mixtures. The polymerization rate with 0.25 mM MgCl2, as judged from shear viscosity, was equal to or greater than that observed with 0.1 M KCl and 0.25 mM MgCl2 at 0 degrees C, and was characterized by a longer nucleation period. Measurements of the turbidity at 350 nm (detecting filament formation and aggregation) and the absorbance at 232 nm (detecting conformational changes of the G-F transition) showed no evidence for polymerization or nucleation in a bulk solution at 0 degrees C when Mg2+ was added to 0.25 mM and, furthermore, F-actin nuclei were ineffective as seeds under these conditions. However, nucleation and polymerization by these criteria could be induced by raising the temperature to 20 degrees C. These results demonstrate the existence of narrow conditions when elongation of F-actin is dissociated from nucleation of oligomeric acceptor nuclei, even if monitored on the sub-molecular level (absorbance at 232 nm). Under these conditions, elongation appears to require anisotropic F-actin, i.e. that filaments are ordered by laminar flow.

Actins↗
PubMed1984

Structural basis and dynamics of the fiber-to-crystal transition of sickle cell hemoglobin.

The kinetics of the assembly of structurally distinct, polymeric aggregates constituting the fiber-to-crystal transition of sickle cell hemoglobin in slowly stirred, deoxygenated solutions has been studied with the use of electron microscopy as a function of pH, as a function of the crystal structures of mutant forms of human deoxyhemoglobins employed as nucleating seeds, and as a function of hemoglobin S chemically modified at the Cys F9 (beta 93) position. The temporal order of appearance of fibers of approximately 210 A diameter, bundles of aligned fibers, macrofibers of greater than or equal to 650 A diameter, and microcrystals is observed. Microscopic fragments of end-stage crystals formed under slowly stirred conditions and introduced as nucleating seeds enhance the rate of crystallization only when added prior to the formation of large bundles of aligned fibers, while microscopic seed crystals added after the formation of bundles of aligned fibers do not alter the rate of crystallization. Over the pH range 6.3 to 7.1, the presence of macrofibers does not influence modulation of the kinetics of the transition with seed crystal fragments. Microscopic seed crystals of deoxyhemoglobin S and deoxyhemoglobin C formed under acidic conditions (pH less than 6.5) have a comparable influence on the kinetics of the fiber-to-crystal transition to that of end-stage crystals. Microscopic seed crystals of deoxyhemoglobin C formed under alkaline conditions (pH greater than 6.5) enhance the formation of macrofibers but do not alter the rate of crystallization. Under conditions associated with enhanced formation of macrofibers, metastable microscopic crystals having axial periodicities of approximately 64 A and approximately 210 A are observed in the intermediate phase of the transition, while end-stage crystals have axial unit cell dimensions identical to those of deoxyhemoglobin S crystallized from polyethylene glycol solutions of pH less than 6.5. Although the metastable crystals may arise from fragments of macrofibers, it is shown that they cannot be transformed directly into end-stage crystals under slowly stirred conditions without undergoing dissolution. These results stipulate that the pathway of the fiber-to-crystal transition proceeds according to the reaction: (Formula: see text) wherein the rate-limiting step is the alignment of fibers into large bundles, and macrofibers are not an intermediate of the fiber-to-crystal transition.(ABSTRACT TRUNCATED AT 400 WORDS)

Crystallization↗
PubMed2003

Generation of prion transmission barriers by mutational control of amyloid conformations.

Self-propagating beta-sheet-rich protein aggregates are implicated in a wide range of protein-misfolding phenomena, including amyloid diseases and prion-based inheritance. Two properties have emerged as common features of amyloids. Amyloid formation is ubiquitous: many unrelated proteins form such aggregates and even a single polypeptide can misfold into multiple forms--a process that is thought to underlie prion strain variation. Despite this promiscuity, amyloid propagation can be highly sequence specific: amyloid fibres often fail to catalyse the aggregation of other amyloidogenic proteins. In prions, this specificity leads to barriers that limit transmission between species. Using the yeast prion [PSI+], we show in vitro that point mutations in Sup35p, the protein determinant of [PSI+], alter the range of 'infectious' conformations, which in turn changes amyloid seeding specificity. We generate a new transmission barrier in vivo by using these mutations to specifically disfavour subsets of prion strains. The ability of mutations to alter the conformations of amyloid states without preventing amyloid formation altogether provides a general mechanism for the generation of prion transmission barriers and may help to explain how mutations alter toxicity in conformational diseases.

Fungal Proteins↗
PubMed1998

Inhibition of growth and aggregation of calcium oxalate crystals in vitro--a comparison of four human proteins.

The aim of this study was to compare directly, in the absence of interfering contaminants, the inhibitory effects of Tamm-Horsfall glycoprotein (THG), human serum albumin (HSA), alpha1-microglobulin and prothrombin fragment 1 (PTF1) on calcium oxalate crystallization. These proteins have been detected in urinary calculi, and with the exception of THG in calcium oxalate crystals generated from undiluted human urine. THG was isolated from the urine of healthy men, while PTF1 was purified from Prothrombinex-HT, a human blood concentrate; HSA and alpha1-microglobulin were obtained from commercial sources. The effects of these proteins were determined, separately, at the same final concentration (32 nM) on calcium oxalate crystallization in a seeded, inorganic reaction system, using Coulter Counter and [14C]oxalate analysis. Analysis of [14C]oxalate data showed that THG, HSA and alpha1-microglobulin had no measurable effect on deposition of calcium oxalate. However, PTF1 significantly inhibited mineral deposition by 19.6%. The average size of the particles precipitated was reduced from the control value of 8.6 microm to 7.3, 5.9, 5.6 and 4.0 microm in the presence of alpha1-microglobulin, HSA, THG and PTF1 respectively. These findings were confirmed by scanning electron microscopy, which also revealed that the smaller particles deposited in the presence of the proteins resulted from reduced crystal aggregation rather than a decrease in the size of the individual crystals. It was concluded that, on a molar basis, PTF1 is a more potent inhibitor of calcium oxalate crystal aggregation than THG, HSA and alpha1-microglobulin. Moreover, unlike those proteins it significantly inhibits the deposition of calcium oxalate. These findings have implications for the putative role of urinary proteins in the formation of calcium oxalate stones.

Alpha-Globulins↗
PubMed1991

Organoid reorganization of human tumors under in vitro conditions.

In the present study we describe a new method to cultivate human tumors, which allows organoid differentiation under in vitro conditions. Diverse tumors of different origin and various histopathology which had been heterotransplanted to athymic mice were dissociated into single cells and seeded at high cell density onto a membrane filter consisting of cellulose nitrate at the gas-medium interface. Within a few days, the tumor cells reorganized and differentiated into organoid structures which exhibited the typical histological characteristics of the original tissues. Due to the formation of organoid aggregates, which was also previously seen with normal fetal cells, this type of culture has been described as 'organoid culture'. In the case of adenocarcinomas of the lung and the colon including the rectum, glandular structures with central lumina, adjacent microvilli, and junctional complexes were formed. Numerous specific intercellular contacts such as desmosomes and tight junctions occurred as well as interdigitations of adjacent cell membranes. In a tumor of the rectum, a typical brush border differentiated at the surface of the reorganized tumor-tissue aggregate. Epidermoid carcinomas of the head and neck developed structures resembling the spinous layer of the epidermis, exhibiting numerous desmosomes and intracytoplasmic bundles of tonofilaments radiating into the desmosomes. Most tumors produced a fragmentary monolayered or multilayered basal lamina of similar morphological appearance as under in vivo conditions. These results illustrate the organoid reorganization and differentiation of human tumor cells under the experimentally rather simple conditions of the organoid culture systems and clearly demonstrate that this in vitro system comes close to the in vivo situation as far as certain differentiation phenomena are concerned.

Adenocarcinoma↗
PubMed2005

Synthesis of monodisperse fluorescent core-shell silica particles using a modified Stober method for imaging individual particles in dense colloidal suspensions.

Core-shell silica particles, with a diameter of 1.5 mum, containing a dye fluorescein isothiocyanate (FITC), are synthesized by the hydrolysis and condensation of tetraethylorthosilicate (TEOS). Sodium dodecyl sulfate (SDS) is added to synthesize fluorescent core particles with the diameter of approximately 1 mum. In the addition of SDS, the surface charge reduced by counterions (Na+) of the surfactant leads to a higher degree of aggregation of the primary particles and the formation of larger secondary particles. The particle growth kinetics confirms the aggregation growth model for the synthesis of monodisperse silica particles, and also shows the dependence of final particle size on colloidal stability resulting from the addition of SDS. Light and X-ray scattering data reveal that the final particles have compactly packed structures with smooth surfaces. The seeded growth technique is then used to form a silica shell layer on the fluorescent core. The added amount of water and NH4OH has significant effects on shell formation. Finally, the final core-shell silica particles are modified by chemisorption of octadecanol at the surface to be dispersed in organic solvents. Octadecyl-coated silica particles are sterically stabilized in silica index-matching solvents such as chloroform and hexadecane to directly image separate particles using confocal microscopy. In chloroform, the organophilic silica particles disperse well, whereas in hexadecane they form a volume-filling gel structure at room temperature.

Journal Article↗
PubMed1998

Characterization of the oligomeric behavior of a 16.5 kDa peanut oleosin by chromatography and electrophoresis of the iodinated form.

Oleosins are amphipathic proteins associated with oil bodies in seeds. We purified the major 16,500 peanut oleosin by preparative SDS-PAGE. Autoradiography after SDS-PAGE separation of the iodinated oleosin revealed covalently bound oligomers with Mr of 21,000, 33,000, 44,000 and 51,000. The strong capacity of these oligomers to form aggregates and to be incorporated into large-sized detergent micelles was demonstrated by gel permeation and isoelectric focusing. A 50% ethanol concentration was necessary to elute the 16,500 oleosin from octyl groups in hydrophobic interaction chromatography showing its natural tendency to interact with lipid acyl chains. This oligomerization behavior in aqueous solution is an indirect reflection of the interactions that occur in the oil body.

Arachis↗
PubMed2001

Yeast [PSI+] "prions" that are crosstransmissible and susceptible beyond a species barrier through a quasi-prion state.

The yeast [PSI(+)] element represents an aggregated form of release factor Sup35p and is inherited by a prion mechanism. A "species barrier" prevents crosstransmission of the [PSI(+)] state between heterotypic Sup35p "prions." Kluyveromyces lactis and Yarrowia lipolytica Sup35 proteins, however, show interspecies [PSI(+)] transmissibility and susceptibility and a high spontaneous propagation rate. Cross-seeding was visualized by coaggregation of differential fluorescence probes fused to heterotypic Sup35 proteins. This coaggregation state, referred to as a "quasi-prion" state, can be stably maintained as a heritable [PSI(+)] element composed of heterologous Sup35 proteins. K. lactis Sup35p was capable of forming [PSI(+)] elements not only in S. cerevisiae but in K. lactis. These two Sup35 proteins contain unique multiple imperfect oligopeptide repeats responsible for crosstransmission and high spontaneous propagation of novel [PSI(+)] elements.

Candida↗
PubMed2005

A structured expert judgment study for a model of Campylobacter transmission during broiler-chicken processing.

A structured expert judgment study was organized to obtain input data for a microbial risk-assessment model describing the transmission of campylobacter during broiler-chicken processing in the Netherlands. More specially, the expert study was aimed at quantifying the uncertainty on input parameters of this model and focused on the contamination of broiler-chicken carcasses with campylobacter during processing. Following the protocol for structured expert judgment studies, expert assessments were elicited individually through subjective probability distribution functions. The classical model was used to aggregate the individual experts' distributions in order to obtain a single combined distribution per variable. Three different weighting schemes were applied, including equal weighting and performance-based weighting with and without optimalization of the combined distributions. The individual experts' weights were based on their performance on the seed variables. Results of the various weighting schemes are presented in terms of performance, robustness, and combined distributions of the seed variables and some of the query variables. All three weighting schemes had adequate performance, with the optimized combined distributions significantly outperforming both the equal weight and the nonoptimized combined distributions. Hence, this weighting scheme, having adequate robustness, was chosen for further processing of the results.

Algorithms↗
PubMed1983

Intracellular occurrence of cowpea mild mottle virus in two unrelated plant species.

The filamentous particles of cowpea mild mottle virus (CMMV) were detected only in the cytoplasm of palisade, mesophyll, parenchyma and epidermal cells of Glycine max (Papilionaceae) and Nicotiana clevelandii (Solanaceae). They were aggregated to form either sheets or bundles or, more frequently, brush-like inclusions. Although CMMV was initially considered to be a possible member of the Carlavirus group, it differs from aphid-borne carlaviruses in its intracellular occurrence and transmission by whiteflies and in being frequently seed-transmitted in some leguminous hosts. Because CMMV is also serologically unrelated to any of 12 recognized carlaviruses, we suggest that it now be removed from the carlavirus group and left unclassified until the taxonomic significance of these differences has been fully evaluated.

Cytopathogenic Effect, Viral↗
PubMed1984

An automated quantitative analysis of ventilation-perfusion lung scintigrams.

We have devised an automated computer analysis of ventilation (Kr-8 1m) and perfusion (Tc-99m) lung images that produces a graphical image of the distribution of ventilation and perfusion, and of ventilation-perfusion ratios. The analysis has overcome the following problems: the identification of the midline between two lungs and the lung boundaries, the exclusion of extrapulmonary radioactivity, the superimposition of lung images of different sizes, and the format for presentation of the data. Therefore, lung images of different sizes and shapes may be compared with each other. The analysis has been used to develop normal ranges from 55 volunteers. Comparison of younger and older age groups of men and women show small but significant differences in the distribution of ventilation and perfusion, but no differences in ventilation-perfusion ratios. Examples are presented to demonstrate that the technique can discriminate between normal and abnormal scintigrams. The analysis of serial images from one individual shows high reproducibility.

Adult↗
PubMed1995

Platelet rebound effect of alcohol withdrawal and wine drinking in rats. Relation to tannins and lipid peroxidation.

We investigated in rats fed a purified diet for 2 and 4 months whether wine drinking was associated with the rebound effect on thrombin-induced platelet aggregation observed after alcohol withdrawal. With 6% ethanol drinking or its equivalent in red or white wine, platelet aggregation was reduced similarly by 70% when the animals drank the alcoholic beverages up to the venipuncture. Depriving the rats of alcoholic beverages for 18 hours was associated with an increase in the platelet response of 124% in those receiving 6% ethanol, of 46% with white wine but a decrease of 59% in those with red wine. The protective effect of red wine on platelets could be reproduced by tannins (procyanidins) extracted from grape seeds or red wine and added to 6% ethanol, but not by glycerol or wine without alcohol. That was related to inhibition of the alcohol-induced lipid peroxidation as shown by the lowering of conjugated dienes, lipid peroxides, and the increase in vitamin E in plasma. Owing to tannins, the platelets of rats drinking red wine did not exhibit the rebound effect observed hours after alcohol drinking, eventually associated with sudden death and stroke in humans.

Alcohol Drinking↗
PubMed1978

Isolation and chemical characterization of a highly purified phytomitogen from Phaseolus coccineus seeds.

An effective lymphocyte mitogen with a low erythroagglutinating ability was isolated from the seeds of Phaseolus coccineus L. by ammonium sulphate precipitation and repeated ion-exchange chromatography on modified Sephadex. The mitogen stimulated lymphocytes at concentrations as low as 0.25 microgram/ml, the optimum concentration being in the range of 2.5-5.0 microgram/ml. This stimulating effect was completely inhibited by 5 mg/ml methyl alpha-D-mannopyranoside. Column gel filtration, disc electrophoresis on polyaceylamide gel in an alkaline medium and in the presence of sodium dodecylsulphate and the finding of a single N-terminal amino acid (alanine) showed the phytomitogen to be homogenous. Disc electrophoresis in an acid medium revealed the presence of two or three bands which are assumed to be due to aggregates of the mitogen. The minimum molecular weight, as derived from sodium dodecylsulphate electrophoresis on polyacrylamide, was 35000. The mitogen is a glycoprotein containing 10% neutral sugars and 1.3% amino sugars (glucosamine). The amino acid composition of the isolated phytomitogen is presented.

Amino Acids↗