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PubMed2005

The chemical constitution and biocompatibility of accelerated Portland cement for endodontic use.

AIM: To evaluate the biocompatibility of mineral trioxide aggregate and accelerated Portland cement and their eluants by assessing cell metabolic function and proliferation. METHODOLOGY: The chemical constitution of grey and white Portland cement, grey and white mineral trioxide aggregate (MTA) and accelerated Portland cement produced by excluding gypsum from the manufacturing process (Aalborg White) was determined using both energy dispersive analysis with X-ray and X-ray diffraction analysis. Biocompatibility of the materials was assessed using a direct test method where cell proliferation was measured quantitatively using Alamar Blue dye and an indirect test method where cells were grown on material elutions and cell proliferation was assessed using methyltetrazolium assay as recommended by the International standard guidelines, ISO 10993-Part 5 for in vitro testing. RESULTS: The chemical constitution of all the materials tested was similar. Indirect studies of the eluants showed an increase in cell activity after 24 h compared with the control in culture medium (P<0.05). Direct cell contact with the cements resulted in a fall in cell viability for all time points studied (P<0.001). CONCLUSIONS: Biocompatibility testing of the cement eluants showed the presence of no toxic leachables from the grey or white MTA, and that the addition of bismuth oxide to the accelerated Portland cement did not interfere with biocompatibility. The new accelerated Portland cement showed similar results. Cell growth was poor when seeded in direct contact with the test cements. However, the elution made up of calcium hydroxide produced during the hydration reaction was shown to induce cell proliferation.

Aluminum Compounds↗

PubMed1993

A role for gamma 3 hordein in the transport and targeting of prolamin polypeptides to the vacuole of developing barley endosperm.

Hordein synthesis, transport and deposition was analysed by immunocytochemistry in developing endosperm cells of wild-type (Carlsberg II) and mutant varieties deficient in B hordein (hor2ca), gamma 1 hordein (Donetsky), gamma 2 hordein and minor B hordein polypeptides (Haisa), or gamma 3 hordein (Nevsky). In all varieties, hordein polypeptides were detected both in the cytoplasm as globules, ranging in diameter from 50 nm to 1.24 microns, and in the vacuole as protein bodies. In the cytoplasmic globules B and C hordein polypeptides are assembled as a core and are surrounded by an outer layer of gamma 1 and gamma 2 hordein. The globules apparently fuse several times in the cytoplasm before entering the vacuole. Absence of gamma 3 hordein in the mutant Nevsky leads to a dramatic change in hordein polypeptide targeting, the hordein storage proteins being largely deposited in the lumen of the rough endoplasmic reticulum. gamma 3 Hordein is unique among the sulphur-rich hordein polypeptides, being monomeric and forming only intramolecular disulphide bridges, while the other B and gamma hordein polypeptides are aggregated by intermolecular disulphide bridges. Retention of hordein in the rough endoplasmatic reticulum in the absence of gamma 3 hordein suggests that gamma 3 hordein may maintain the prolamin storage polypeptides in a transport competent state. The sequence of the mature gamma 3 hordein polypeptide was deduced from a cDNA clone, and compared with gamma 2 hordein. The epitope recognized by the gamma 1 + gamma 2 hordein-specific BX monoclonal antibody used for immunocytochemistry was mapped to include E190 and K193, by synthesizing overlapping oligopeptides.

Amino Acid Sequence↗

PubMed2001

Hantavirus nucleocapsid protein oligomerization.

Hantaviruses are enveloped, negative-strand RNA viruses which can be lethal to humans, causing either a hemorrhagic fever with renal syndrome or a hantaviral pulmonary syndrome. The viral genomes consist of three RNA segments: the L segment encodes the viral polymerase, the M segment encodes the viral surface glycoproteins G1 and G2, and the S segment encodes the nucleocapsid (N) protein. The N protein is a 420- to 430-residue, 50-kDa protein which appears to direct hantavirus assembly, although mechanisms of N protein oligomerization, RNA encapsidation, budding, and release are poorly understood. We have undertaken a biochemical and genetic analysis of N protein oligomerization. Bacterially expressed N proteins were found by gradient fractionation to associate not only as large multimers or aggregates but also as dimers or trimers. Chemical cross-linking of hantavirus particles yielded N protein cross-link products with molecular masses of 140 to 150 kDa, consistent with the size of an N trimer. We also employed a genetic, yeast two-hybrid method for monitoring N protein interactions. Analyses showed that the C-terminal half of the N protein plus the N-terminal 40 residues permitted association with a full-length N protein fusion. These N-terminal 40 residues of seven different hantavirus strains were predicted to form trimeric coiled coils. Our results suggest that coiled-coil motifs contribute to N protein trimerization and that nucleocapsid protein trimers are hantavirus particle assembly intermediates.

Amino Acid Motifs↗

PubMed1994

Reversible random coil-beta-sheet transition of the Alzheimer beta-amyloid fragment (25-35).

The beta-amyloid protein (39-43 amino acid residues) is the major constituent of the amyloid deposits found in brain of patients with Alzheimer's disease. Using circular dichroism spectroscopy, we have studied the secondary structure and the aggregation of fragment 25-35 of the beta-amyloid protein (beta AP(25-35)OH) under a variety of conditions. beta AP(25-35)OH in solution at pH 4.0 or 5.5 exhibits a concentration-dependent random coil<-->beta-sheet transition. The equilibrium is characterized spectroscopically by an isodichroic point and can be described quantitatively by a simple association model with association constants between 1.8 x 10(4) M-1 (non-cooperative model, nucleation parameter sigma = 1) and 2.9 x 10(4) M-1 (cooperative model, sigma = 0.2). The enthalpy of association is delta H approximately -3 kcal/mol as determined by titration calorimetry. The equilibrium is shifted completely toward beta-structured fibrils at pH 7.4 where the Met-35 carboxyl group is fully charged. In contrast, removal of the charged carboxy terminus by amidation locks the equilibrium in the random coil conformation. Model calculations suggest an antiparallel beta-sheet structure involving residues 28-35 which is stabilized at both ends of the beta-sheet by ion pairs formed between Lys-28 and Met-35. Removal of fibrils via millipore filtration leads to solutions with random coil monomers only. Seeding these solutions with a few fibrils establishes a new random coil<-->beta-sheet equilibrium.

Alzheimer Disease↗

PubMedDate not supplied

Surface morphology of circulating platelets: a suggested parameter for the monitoring of endothelial seeded grafts.

For the clinical follow-up of endothelial cell seeded grafts, non-invasive but sensitive parameters are required in order to determine the extent and effectiveness of the endothelialization process. Such a very sensitive parameter was found by investigating the surface morphology of circulating platelets. This technique is based on the previous observation that characteristic alterations of platelet morphology are closely associated with the course of the aggregometer tracings. Applying these ultrastructural criteria we investigated 16 patients after distal femoro-popliteal and femoro-crural bypass surgery. Reinforced 6 mm non-seeded PTFE vascular grafts were compared with reversed autologous saphenous vein grafts. As early as 4 hours after graft implantation, a significant higher percentage of discoid platelets with marginal pseudopods--representing the earliest stage of platelet activation--as well as of spheroid "shape changed" platelets was found in patients with PTFE grafts. Moreover, perforated platelet membranes were exclusively found in the PTFE group. These findings were most distinguished 10 days postoperatively but persisted over the follow-up period of 1 year. Considering the sensitivity of the described technique it might provide a simple, reliable, and non-invasive means for the clinical assessment of successful graft endothelialization.

Blood Platelets↗

PubMed1985

Characterization of Lotus tetragonolobus fucolectin components for differences in hemagglutinating and macrophage activating activities.

The fucose binding proteins (FBP) extracted from Lotus tetragonolobus seeds were isolated by affinity chromatography and compared with affinity purified commercial preparations for physical, antigenic, and biological properties. All preparations contained three protein components as determined by polyacrylamide gel electrophoresis, each with a subunit molecular weight of approximately 27 Kd. FBP preparations were also found to be antigenically identical by immunodiffusion analysis and possessed similar biological activities for hemagglutination of group 0 erythrocytes and macrophage activation in the migration inhibition assay. A reversible temperature dependent hemagglutination characteristic was found; FBP agglutinated erythrocytes at 4 degrees and 22 degrees C but not at 37 degrees C, which was reversed by decreasing the incubation temperature from 37 degrees C to 22 degrees C. Temperature dependent binding of FBP for macrophages was also demonstrated. Adsorption of crude FBP by group 0 erythrocytes preferentially removed hemagglutinin without loss of macrophage activating properties. Similarly adsorption of FBP with macrophages preferentially removed macrophage activating component. Separation of the lectin components by DEAE cellulose chromatography yielded two major fractions: a potent hemagglutinin with weak macrophage activating properties and a potent macrophage activator with weak hemagglutinating activity. Separation of the crude lectin by ultrafiltration indicated that the macrophage activating component exists in a highly aggregated form which may determine its macrophage activating properties. Our results indicate that L. tetragonolobus consists of two distinct classes of components which correspond to tetrameric glycoproteins of 118-120 Kd with potent temperature dependent hemagglutinating activity and a highly aggregated dimeric component of 58 Kd with macrophage activating properties.

ABO Blood-Group System↗

PubMed2005

Effect of transition metals (Mn, Cu, Fe) and deoxycholic acid (DA) on the conversion of PrPC to PrPres.

The PMCA (protein misfolding cyclic amplification) technique has been shown to drive the amplification of misfolded prion protein by PrP(Sc) seeds during several cycles of incubation-sonication. Here, we report that cyclic amplification of normal hamster brain homogenates treated with a number of transition metals (manganese [Mn], copper [Cu], and iron [Fe]) leads to conversion of PrP(C) into protease-resistant PrP(res). The efficiency of PrP(res) formation and the glycoforms induced by Mn were different from those obtained by Cu and Fe. Previous results have shown higher Mn and lower Cu levels in the affinity-purified PrP(Sc) from the brain of prion diseases compared with normal hamster brain homogenates. We focused on Mn because we observed higher levels of Mn in whole brain, mitochondria, and scrapie-associated fibril-enriched fractions from the brains of animals with prion disease. In the presence of minute quantities of Mn-induced PrP(res) template with a large amount of PrP(C), PrP(res) amplification is observed. A metal chelater, EDTA reverses the effect of Mn on PrP(res) amplification, suggesting that Mn may play a role in the formation of PrP(res). It has been proposed that metal-catalyzed oxidation of PrP leads to the oxidation of amino acids and extensive aggregation of oxidized PrP. Carboxyl acids such as deoxycholic acid (DA) are oxidized molecules produced by 3' oxidation pathway. In in vitro studies, the potent effect of Mn on PrP(res) amplification is augmented by DA in a dose-dependent manner. On the basis of the evidence of the elevated Mn levels in scrapie-associated fibril (SAF)-enriched preparations from the brains of animals with prion disease, Mn-loaded PrP and oxidized molecules such as carboxyl acids may contribute to the formation of the scrapie isoform of PrP in prion diseases.

Animals↗

PubMed1988

The Fc gamma receptor of natural killer cells is a phospholipid-linked membrane protein.

Three types of receptor for the Fc (constant) region of human immunoglobulin G have been described; FcRI, a high-affinity (Ka approximately equal to 10(8) M-1) receptor expressed on monocytes; FcRII (CD32), a low-affinity (Ka approximately equal to 10(6) M-1) receptor expressed on B cells, granulocytes, macrophages and platelets; and FcRIII (CD16, FcRIo), a low-affinity receptor expressed on macrophages, neutrophils, eosinophils, natural killer cells and a subset of T cells believed to comprise the suppressor cells. Anti-CD16 antibodies block natural killer-cell mediated antibody dependent cellular cytotoxicity (ADCC). Binding of aggregated IgG to CD16 on natural killer cells leads to the expression of lymphocyte activation antigens, mediator release, morphological changes and lytic activity. We report here the isolation of a complementary DNA clone encoding CD16 determinants which gave rise to IgG binding of the expected affinity and subtype specificity in COS cells, and which proved to encode a phospholipid anchored protein. A single messenger RNA transcript was found in all positive RNA samples, and N-glycanase treatment showed the form found in COS cells was identical to the form present on peripheral blood mononuclear cells (PBMCs). We also show that CD16 is most closely related to the alpha-form of the murine IgG 2b/1 receptor and propose that extracellular contacts mediate the signal initiated by IgG binding.

Amino Acid Sequence↗

PubMed1997

Application of glutaraldehyde-crosslinked chitosan as a scaffold for hepatocyte attachment.

The effectiveness of chitosan, a biocompatible polymer derived by the deacetylation of chitin, as a scaffold of hepatocyte attachment, was examined. Since chitosan gel was too fragile to use for cell culture, its free amino groups were crosslinked by glutaraldehyde to increase its strength. Rat hepatocytes seeded onto glutaraldehyde-crosslinked chitosan (GA-chitosan) gel could stably attach to the surface, retaining its spherical form, the same as in vivo, and then release a very small amount of lactate dehydrogenase during the 5 d culture period. By contrast, hepatocytes on a collagen-coated surface spread flat, and they released much more lactate dehydrogenase than those on the GA-chitosan gel. Hepatocytes on GA-chitosan also retained higher urea synthesis activity, a liver-specific function, than those on the collagen-coated surface. These results indicate that chitosan is a promising biopolymer as a scaffold of hepatocyte attachment, which can be applied to an effective bioartificial liver support system.

Animals↗

PubMed2006

Cytosolic proteins regulate alpha-synuclein dissociation from presynaptic membranes.

Intracellular accumulation of insoluble alpha-synuclein in Lewy bodies is a key neuropathological trait of Parkinson disease (PD). Neither the normal function of alpha-synuclein nor the biochemical mechanisms that cause its deposition are understood, although both are likely influenced by the interaction of alpha-synuclein with vesicular membranes, either for a physiological role in vesicular trafficking or as a pathological seeding mechanism that exacerbates the propensity of alpha-synuclein to self-assemble into fibrils. In addition to the alpha-helical form that is peripherally-attached to vesicles, a substantial portion of alpha-synuclein is freely diffusible in the cytoplasm. The mechanisms controlling alpha-synuclein exchange between these compartments are unknown and the possibility that chronic dysregulation of membrane-bound and soluble alpha-synuclein pools may contribute to Lewy body pathology led us to search for cellular factors that can regulate alpha-synuclein membrane interactions. Here we reveal that dissociation of membrane-bound alpha-synuclein is dependent on brain-specific cytosolic proteins and insensitive to calcium or metabolic energy. Two PD-linked mutations (A30P and A53T) significantly increase the cytosol-dependent alpha-synuclein off-rate but have no effect on cytosol-independent dissociation. These results reveal a novel mechanism by which cytosolic brain proteins modulate alpha-synuclein interactions with intracellular membranes. Importantly, our finding that alpha-synuclein dissociation is up-regulated by both familial PD mutations implicates cytosolic cofactors in disease pathogenesis and as molecular targets to influence alpha-synuclein aggregation.

Animals↗

PubMed1990

Structural studies on native and chemically modified storage proteins from rapeseed (Brassica napus L.) and related plant proteins.

Recent data on the structure and chemical modification of the two main storage proteins of rapeseed, the high-molecular mass 12 S globulin and the low-molecular mass 2 S protein (napin) are summarized and compared with those of related seed proteins. The 12 S globulin is built up of six subunits forming a quaternary structure which can be approximated by the model of a trigonal antiprism. The subunits, composed of a larger and a smaller polypeptide chain each, have a two-domain structure which is typical for all related plant proteins. These are characterized by a sedimentation coefficient of 11-13 S, a molecular mass of 300,000-360,000 g/mol and a high percentage of beta-sheet conformation. Increasing succinylation results in a step-by-step dissociation up to the subunits and to an unfolding of the latter at a critical level of modification amounting to 60-70%. These structural changes affect the functional properties remarkably. The napin fraction comprises a group of closely related and highly basic proteins with molecular masses of 12,000-14,000 g/mol, a high content of sulphur-containing amino acids and rich in helical conformation. They are built up of a larger and a smaller disulphide bridged polypeptide chain. Acylation does not abolish the secondary or tertiary structure which are stabilized by inter- and intrachain disulphide bonds. Acylation results, however, in a stabilization of the protein against heat-induced aggregation.

2S Albumins, Plant↗

PubMed1987

The influence of linoleate and vitamin E from sunflower seed oil on platelet function and prostaglandin production in the common marmoset monkey.

Vitamin E and linoleate, both of which are found in high concentrations in sunflower seed oil, were examined independently for their influence on general and blood-vascular parameters in vitamin E-deficient common marmosets. A vitamin E-deficient diet (-E, 4 micrograms/g) was supplemented with either 40 micrograms/g vitamin E (+E), vitamin E stripped sunflower oil (+10% SSO-E), or SSO (+10% SSO w/w) in a 2 x 2 factorial designed experiment, and the diets fed for 9 months to 4 even groups of common marmosets. Vitamin E deficiency was associated in marmosets with a loss of skeletal muscle mass and of body weight, enhanced peroxidative haemolysis of erythrocytes, increased white blood cell counts, and in the SSO-E group a relative neutrophilia. Platelet reactivity was increased with vitamin E deficiency, and to a greater degree with the SSO-E group. Aortic prostacyclin production was significantly increased by the addition of vitamin E, linoleate and both as SSO to the deficient diet, the effects being additive. Fatty acid changes associated with the different treatments reflected the influence of high linoleate and vitamin E treatments. The platelet and aortic arachidonate value in the SSO-E group showed the lowest and most variable value, and this was associated with greatest platelet aggregability. An adequate vitamin E intake is essential for stabilising high PUFA diets and biomembranes and enhancing the protective role of prostacyclin in blood vessels against thrombogenesis.

Animals↗

PubMed2004

Effects of protein engineering of canola procruciferin on its physicochemical and functional properties.

The primary structure of Brassica napus procruciferin 2/3a was engineered to elucidate structure-function relationships and to improve the functionality of cruciferin. The following mutants were constructed: (1) C287T, (2) DeltaII, variable region II was deleted; (3) C287T/DeltaII, mutation involving (1) and (2); (4) DeltaIV + A1aIV; and (5) DeltaIV + A3IV, variable region IV was replaced with variable region IV containing many charged residues from soybean glycinin A1aB1b and A3B4 subunits. Differential scanning calorimetry analysis revealed that the A1aIV region has a more favorable interaction with the procruciferin molecule than does A3IV as well as the original regions. On the basis of heat-induced precipitation analysis, it was concluded that replacement of the free cysteine residue with threonine (C287T) and insertion of charged regions (DeltaIV + A1aIV and DeltaIV + A3IV) could lead procruciferin to form soluble aggregates after heating. Low solubility was observed in mutants DeltaIV + A3IV, DeltaII, and C287T/DeltaII, especially between pH 4 and 6 at mu = 0.08, but not in DeltaIV + A1aIV, indicating that the number of acidic amino acid residues and the high number of glutamine residues are important factors for solubility at mu = 0.08. None of the mutants showed any improvements in emulsifying ability, indicating that destabilization and addition of the hydrophilic region are not effective for emulsification. The insertion of the A1aIV region in procruciferin made the molecule more susceptible to alpha-chymotrypsin.

Allergens↗

PubMed1994

Seeded growth of hydroxyapatite in the presence of dissolved albumin at constant composition.

Hydroxyapatite (HAP) crystals were grown from a supersaturated solution by the addition of seed crystals at a temperature of 37 degrees C. Throughout the experiment, the pH and calcium ion concentration were monitored by electrodes in the solution, and maintained at constant values by the addition of ammonia solution (maintaining a pH value of 7.4 during HAP precipitation) and calcium nitrate solution. Triammonium orthophosphate solution was added at the same time as calcium nitrate, so that the ratio of calcium to phosphate ions in the solution was appropriate to the precipitation of HAP. The volume of calcium nitrate solution which needed to be added was used as a measure of HAP crystal growth. Albumin was added to some of the supersaturated solutions to give a concentration in the range 50-250 micrograms cm-3. HAP crystals grown at different albumin concentrations were examined by scanning electron microscopy. After an initial period of 30 min, the growth of HAP crystals increased linearly with time. This behavior was attributed to initial growth healing such dislocations as steps and kinks; growth at screw dislocations was considered to occur throughout the period of the experiment and to give rise to the linear growth phase. The linear growth rate decreased linearly with the albumin concentration. HAP crystals grown in the absence of albumin formed spherical aggregates; the size of these aggregates decreased with the albumin concentration.

Calcium↗

PubMedDate not supplied

Control of cellular organization in three dimensions using a microfabricated polydimethylsiloxane-collagen composite tissue scaffold.

Parallel channels of various dimensions have been shown to cause a monolayer of cells in culture to align in the direction of the channels. For the engineering of complex organ systems to become a reality, similar control over the cellular microenvironment in three dimensions must be achieved. Using microfabrication, a polydimethylsiloxane (PDMS) scaffold (40 microm wide, 70-microm-deep parallel channels separated by 25-microm-wide walls) was created. A fibroblast-seeded collagen matrix was then molded around this PDMS scaffold. The PDMS scaffold served as an internal skeleton to guide the cells to grow in the prescribed three-dimensional pattern. Organization, aspect ratio, and the z diameter of the cells were analyzed by confocal microscopy. Fibroblasts elongated and organized in the direction of the channels throughout the height of the scaffold. The mean angle of the cells off of the long axis of the channels was 4.3 +/- 0.7 degrees as opposed to 32.6 +/- 2.2 degrees in controls. The morphology of the cells was also affected by the PDMS scaffold. The nuclei were longer (1.25x) and thinner (0.75x) than in control gels; however, no changes in diameter of the cells in the z direction were seen.

Biocompatible Materials↗

PubMedDate not supplied

Microtubule assembly in Friend erythroleukemia cells spread on fibronectin- and lectin-coated substrates.

A comparison was carried out between parental Friend Erythroleukemia cells (FLC, 745 A clone) and highly fibronectin (FN)-sensitive clones of FLC for their ability to adhere, spread and organize microtubular (MT) apparatus, when seeded on FN- or lectin-coated plastic substrates. While FN was able to induce the spreading only in the FN-sensitive FLC clones (further referred to as FF clones) and not in the parental 745 A cells, the lectins Concanavalin A (ConA) and Leukoagglutinin (LeuA) promoted the spreading of both 745 A and FF cells, with no differences between the two cell lines. Wheat germ agglutinin (WGA), instead, is almost ineffective in triggering cell spreading in both cell clones. The spreading of FLC, either 745 A or FF, on any of the ligands tested, is always accompanied by a massive reorganization of the MT apparatus of the cell. Possible mechanisms involved in the selective spreading effect, exerted by FN, are discussed.

Agglutinins↗

PubMed1993

[Extraction and characterization of zeins from kernels of 10 maize cultivars].

The study consisted in the extraction and characterization of zeins of Venezuelan maizes, according to their solubility and molecular properties. The cultivars analyzed were the hybrids Ceniap PB8, Tocoron 127, Arichuna, Obregón, Ceniap 3, Corocito 101 and the varieties Máquina del Ceniap, Venezuela-1 and Venezuela-1 Opaco-2. Zeins were extracted with 70% ethanol and fractionated by two methods: 95% ethanol and column filtration with Sephadex G-200. The molecular weight was determined by electrophoresis in a discontinuous polyacrilamide gel with sodium dodecyl sulfate (PAGE-SDS). The results demonstrated that zeins account for 36.57% of the total protein present in normal corn grain and 9.38% in Opaque-2 corn. Prolamines presented a soluble fraction in 95% ethanol (alpha zeins) which represented 33,12% of zeins and another insoluble (beta zeins) the 66.88%. In column fractionation, three fractions were obtained, two major A and C and another B in minor quantity, which varied in proportion between cultivars. Zeins which were reduced with 2-mercaptoethanol separated into two subunits with molecular weights of 21,300 and 24,300 daltons, whereas unreduced zeins presented large sized aggregates which remained at the origin and large numbers of bands (nine) whose molecular weights oscillated between 24,300 and 87,000 daltons. The electrophoretic patterns of normal maizes were similar, but differ from the pattern of the Opaque-2. In this maize, zeins reduced presented only the band with molecular weight 24,300 daltons and the unreduced zeins showed those with molecular weights of 87,000; 78,500; 48,500 and 24,300 daltons. Reduced alpha and beta are made up of the same basic components of zeins. Likewise unreduced alpha zeins are made up of the same polypeptides as unreduced zeins. The difference between Opaque-2 zeins and normal ones in that they contain more alpha zeins and less polypeptides of high molecular weight.

Chromatography, Gel↗

PubMed2006

Polysomes are associated with microtubules in fertilized eggs of Chinese pine (Pinus tabulaeformis).

Transmission electron microscopy of immunogold-labeled Chinese pine egg cells before and after fertilization revealed that polysomes are associated with microtubules (MTs) from fertilization to the 2-nucleate embryo stage. Ribosome aggregates of various size and shape were randomly distributed in the cytoplasm of the eggs before fertilization. Single MTs or clusters were observed to be free of polysomes at this stage. Upon fertilization, all polysomes were attached to MTs, and this association persisted until the formation of the polarized embryo. Thereafter, the polysomes spread into the cytoplasm and no polysome-MT association was observed in the embryo. Some of the polysomes were attached to one end of the MTs, while others appeared to form contacts along their entire length. No polysome-microfilament association was observed at any stage of the development. The polysome-MT association may provide a mechanism for MT-dependent mRNA localization in early embryo development of this plant.

Cell Polarity↗