DETECTION OF SILICA IN PLANTS

Silica in plants can be stained by silver Chromate, methyl red, and a colorless crystal violet lactone which are adsorbed by the silanol groups resulting in red-brown, red, and blue colors, respectively. Specialized silica cells in grasses can also be detected through polarization colors due to form birefringence. Silica in the bulliform and silica cells of rice leaves is amorphous and is made up of 1–2-nm particles aggregating into 2.5 X 0.4-μm rods with oblique ends.     

Pine cone-mediated green synthesis of silver nanoparticles and their antibacterial activity against agricultural pathogens

The medicinal and physicochemical properties of nanoscale materials are strong functions of the particle size and the materials used in their synthesis. The nanoparticle shape also contributes significantly to their medicinal properties. Several shapes ranging from oval, spherical, rods, to teardrop structures may be obtained by chemical methods. Triangular and hexagonal nanoparticles have been synthesized by using a pine cone extract (PCE). Here, we report the discovery that PCE, when reacted with silver nitrate ions, yields a high percentage of thin, flat, single-crystalline nanohexagonal and nanotriangular silver nanoparticles. The nanohexagonal and nanotriangular nanoparticles appear to grow by a process involving rapid reduction with assembly at room temperature at a high pH. The nanoparticles were characterized by UV–Vis absorption spectroscopy, SEM-EDS, TEM, FTIR, and X-ray diffraction analyses. The anisotropy of the nanoparticle shape results in large near-infrared absorption by the particles. Highly anisotropic particles are applicable in various fields, including agriculture and medicine. The obtained silver nanoparticles (Ag NPs) had significant antibacterial action on both Gram classes of bacteria associated with agriculture. Because the Ag NPs are encapsulated with functional group-rich PCE, they can be easily integrated in various applications.     

Location of diazotrophs in the root interior with special attention to the kallar grass association

There is increasing evidence that nitrogen-fixing bacteria are able to colonize the interior of grass roots. Several techniques have been used to demonstrate the sites of colonization and are discussed. Among the techniques useful for specific labelling, gold-labelled reagents have been frequently successfully applied in other fields. We propose the use of the protein A-gold technique coupled with silver amplification and light microscopy to render diazotrophs visible in semi-thin sections of roots, and we have applied this technique to gnotobiotically grown kallar grass. LR white resin soft grade was a suitable resin for embedding. Diazotrophic rods predominating in the endorhizosphere of naturally growing kallar grass had the potential to colonize the aerenchyma of gnotobiotically-grown plants. Penetration by the bacteria probably occurred at epidermal cell junctions and at points of emergence of lateral roots, as also proposed forAzospirillum. Larger cell aggregates described by us for naturally occurring kallar grass plants were not detected in the gnotobiotic system. Physiological consequences of colonization of the aerenchyma are discussed.     

Transport properties of rigid bent-rod macromolecules and of semiflexible broken rods in the rigid-body treatment. Analysis of the flexibility of myosin rod.

The translational diffusion coefficients, rotational relaxation times and intrinsic viscosities of rigid bent rods, composed by two rodlike arms joined rigidly at an angle alpha, have been evaluated for varying conformation using the latest advances in hydrodynamic theory. We have considered semiflexible rods in which the joint is an elastic hinge or swivel, with a potential V(alpha) = 1/2Q alpha 2 with constant Q. Accepting the rigid-body treatment, we calculate properties of broken rods by averaging alpha-dependent values for rigid rods. The results are finally used to interpret literature values of the properties of myosin rod. Q is regarded as an adjustable parameter, and the value fitted is such that the average bending angle of myosin rod is approximately 60 degrees.     

Ontogeny of the photoreceptors in the embryonic retina of the viviparous guppy,Poecilia reticulata P. (Teleostei)

Summary Ultrastructural analyses of retinal development in the guppy embryo show that at midgestation all types of photoreceptors are differntiated in the fundus, and at birth differentiation extends over the whole retina. Formation of discs of outer segments is more rapid in rods than in cones. Double cones differentiate simultaneously with long single cones and are formed by the adhesion of two primordial inner segments; short single cones develop last. Wherever cones are differentiated, they are arranged in an adult-type square mosaic. The rods in the embryo, as opposed to the adult, are likewise regularly arranged within the mosaic unit.These results are at variance with the generally held opinion that adult teleosts which possess duplex retinae have larvae with pure cone retinae, and that rods, double cones and mosaics appear in late larval life or only at metamorphosis.In the double cones of the guppy embryo subsurface cisternae develop along the adjoining primordial inner segments. Additionally, regularly distributed subsurface cisternae are formed in the regions of intimate contact of long single cones with double cones and rods.We suggest that the early development of rods and double cones, and a square-mosaic with regular distribution of rods and subsurface cisternae, provide the newly born with a fully functional optical apparatus, especially suited to perception of movements. This is necessary for its survival against predatory, especially maternal, attacks.This work was in part subsidized by a grant from the Medical Research Council of Ireland to Y.W.K.     

Behavior of peripheral rods and their role in the life cycle of Myxococcus xanthus.

Myxococcus xanthus is a gram-negative bacterium with a complex life cycle including a developmental phase in which cells aggregate and sporulate in response to starvation. In previous papers, we have described a heretofore unsuspected layer of complexity in the development of M. xanthus: vegetatively growing cells differentiate into two cell types during development. In addition to the differentiation of spores within fruiting bodies, a second cell type, peripheral rods, arises outside fruiting bodies. The pattern of expression of proteins in peripheral rods is different from that of either vegetatively growing cells or spores, and peripheral rods express a number of recognized developmental markers. In this report, we examine four aspects of the biology of peripheral rods: (i) the influence of nutrients on the proportion of peripheral rods in a population of developing cells, (ii) the capacity of peripheral rods to recapitulate development, (iii) the development of peripheral rods on conditioned medium, and (iv) the ability of peripheral rods to resume growth on low amounts of exogenously added nutrients. The results of these studies suggest that peripheral rods play a significant role in the life cycle of M. xanthus by allowing the exploitation of low amounts or transient influxes of nutrients without the investment of energy in spore germination. The differentiation of vegetatively growing cells into two cell types that differ significantly in biology, shape, and localization within the population has been incorporated into a model of the life cycle of M. xanthus.     

A Physical Method for Deriving the Electrostatic Interaction between Rod-Like Polyions at All Mutual Angles

The screened Coulomb interaction between polyelectrolyte cylinders immersed in an ionic bath is examined. The electrostatic force and torque acting between a pair of unlike rods is formulated for all separations in which the electrostatic potential on some dividing surface between rods can be written as a linear superposition of isolated cylinder potentials. (The surface potential on the rods themselves may be much higher than that permitted by a superposition approximation.) The mutual energy in the case of skewed rods is found to be exponential in separation and proportional to 1/sin θ where θ is the twist angle of one rod relative to the other. Rods with similar charge repel each other with a torque acting to make the rods perpendicular while rods of opposite charge attract with the parallel arrangement preferred.     

Assembly of tobacco mosaic virus in vitro. Improved model for the elongation process by protein subunits.

The in vitro assembly reaction of tobacco mosaic virus (TMV), especially the elongation process of partially reconstituted RNA (PRR) by protein subunits, was observed by electron microscopy. After addition of TMV-protein subunits, the PRR appeared as rods with a clump at one end, believed to be a complex between added protein subunits and the RNA tail protruding from PRR. The subunits entrapped on the RNA tails in the forms of clumps were progressively incorporated into the growing rods on incubation, ending with the formation of completely reconstituted rods. The clumps were also observed after addition of cucumber green mottle mosaic virus (CGMMV) protein subunits to rods partially reconstituted from RNA and TMV-protein. In this case, the protein subunits, seen as clumps, did not become incorporated to form elongating rods. An improved model for the elongation of TMV rods is proposed. The elongation process is composed of two steps, with the first step being the interaction of protein subunits with the RNA tail protruding from the growing rod. Any protein having a specific binding site for TMV-rna, not limited to TMV-protein, will react in the first step. The second step is the incorporation of the protein on the RNA tail into a rod-shaped structure, with consequent elongation of the growing rod. It appears that only protein homologous with that in the partially reconstituted rods can partake in the second step.     

Hereditary abnormality in tapetum lucidum of the Siamese cats

Summary Gross examination showed a weaker reflection (less shining) of the tapetum lucidum of the Siamese cats compared with common cats. Toluidine blue sections revealed that many tapetal cells were weakly stained and giving vacuolated appearance under high magnification. Further examination with electron microscope showed that those weakly stained cells were filled with disrupted tapetal rods. In these affected cells, the arrangement of the tapetal rods was no longer regular. The membranes of the tapetal rods were either enlarged or disrupted. Some of them appeared to be myelin-like structures. The cores of the tapetal rods were either empty or filled with electron-dense materials which may be the remnant of the original cores. The severity of this type of abnormality or degeneration in the tapetum varied from lavers to layers. Those layers closer to the retina showed a greater number of cells with degeneration. Quantitative analysis of histochemical detection of zinc showed a significantly smaller amount of zinc in tapetal rods of the Siamese cats as compared with common cats. Less zinc and disruption of the regular arrangement of the tapetal rods may result in weaker reflection of light by Siamese cat tapetum. In four of the nine Siamese cats studied, this type of abnormality was observed. It suggests that it is a hereditary disorder of relatively high frequency.     

Fine structure of the retinal photoreceptors of the ranch mink Mustela vison

The structure of the retinal photoreceptors of the ranch mink (Mustela vison) has been investigated by light and electron microscopy. In this mammalian species, the photoreceptors can be readily differentiated and adequately described by the classical terminology of rods and cones, with the rods being the more numerous. Rods are long slender cells while cones are shorter and stouter in appearance. Both rods and cones are highly differentiated and extremely polarized cells consisting of an outer segment, a non-motile connecting cilium, an inner segment, a nuclear region and a synaptic process extending to an expanded synaptic ending. Morphological differences are noted between rods and cones for most of the various regions of these cells. While rods reach to the cell body of the retinal pigment epithelial (RPE) cells, larger apical processes from the RPE extend to the shorter cone cells, so that both photoreceptor types are in intimate contact with the retinal epithelial cells.     

Conformational stability of the myosin rod

Chymotryptic cleavage patterns of myosin rods from pig stomach, chicken gizzard, and rabbit skeletal muscle indicate that short (approximately 45 nm) heavy meromyosin subfragment 2 (SF2) is a consistent product of all three rods, whereas long (approximately 60 nm) SF2 is derived only from skeletal muscle myosin. Differential scanning calorimetry was used to follow the thermally induced melting transition of the rods and certain of their subfragments. In 0.12 M KCl, sodium phosphate buffer, pH 6.2-7.6, the light meromyosin (LMM) and SF2 domains of each rod had essentially identical conformational stabilities. Temperature midpoints for the melting transitions were 54-56 degrees C for the two smooth muscle myosin rods and 50-53 degrees C for the skeletal muscle myosin rod. In 0.6 M K Cl buffer, melting transitions for the smooth muscle myosin rods were essentially unchanged, but skeletal muscle myosin rods showed multiphase melting, with major transitions at 43 degrees C and 52 degrees C. The first of these was tentatively attributed to LMM, and the second to SF2. In 0.12 M K Cl buffer, the LMM transition was stabilised so that it superimposed on that of SF2. No melting was observed in any of the rods at physiological temperature. These results indicate that, excluding a possible but only narrow hinge region, the entire myosin rod has essentially uniform conformational stability at physiological pH and ionic strength, and thus that the contractile and elastic properties of the cross-bridge exist in the heavy meromyosin subfragment 1 (SF1) domains of the molecule.     

Molecular architecture of the neurofilament. I. Subunit arrangement of neurofilament L protein in the intermediate-sized filament

Using the smallest subunit (NF-L) of a neurofilament and a glial fibrillary acidic protein, the subunit arrangement in intermediate filaments was studied by low-angle rotary shadowing. NF-L formed a pair of 70 to 80 nm rods in a low ionic strength solution at pH 6.8. Two 70 to 80 nm rods appeared to associate in an antiparallel manner with an overlap of about 55 nm, almost the same length as the alpha-helix-rich central rod domain of intermediate filament proteins. The overlap extended for three-beaded segments, present at 22 nm intervals along the pairs of rods. The observations that (1) 70 to 80 nm rods were a predominant structure in a low ionic strength solution at pH 8.5, (2) the molecular weights of the rod and the pair were measured by sedimentation equilibrium as 190,000 and 37,000 respectively, and (3) the rods formed from the trypsin-digested NF-L had a length of about 47 nm, indicated that the 70 to 80 nm rod is the four-chain complex and the pair of rods is the eight-chain complex. Similar structures were observed with glial fibrillary acidic protein, indicating that these oligomeric structures are common to other intermediate filament proteins. NF-L assembled into short intermediate-sized filaments upon dialysis against a low-salt solution containing 1 to 2 mM-MgCl2 at 4 degrees C. The majority of these short filaments possessed four or five-beaded segments, suggesting that the pair of rods were arranged in a half-staggered fashion in neurofilaments. On the basis of these observations, we propose the following model for the intermediate filament subunit arrangement. (1) The four-chain complex is the 70 to 80 nm rod, in which two coiled-coil molecules align in parallel and in register. (2) Two four-chain complexes form the eight-chain complex by associating in an antiparallel fashion with the overlap of the entire central rod domain. (3) The eight-chain complex is the building block of the intermediate filament. The eight-chain complexes are arranged in a half-staggered fashion within the intermediate filament.     

A new technique for the surgical management of deformities in the growing spine.

The Luque procedure was developed to correct the deformity without the need of bracing and maintaining that correction with growth. However many authors are disappointed by their results and the complications which appear in the management of infantile scoliosis with Luque trolley alone. Besides failed implants, pseudarthrosis, modest spinal growth and protuberant rods and wires, the major problem of the Luque systems is the high incidence of loss of correction by postoperative rotation. Therefore a new application technique is recommended. A standard posterior extraperiostal approach is chosen. Sublaminar titanium cables are passed at each level except the caudal lamina. Then the rods are precontoured in shape of the planed curve correction. We use a low profile titanium instrumentation with 5.0 mm diameter rods and 4.2 mm pedicle screws. In contrast to the conventional use of two antiparallel "L"-rods we recommend the use of one reversed "U"-rod securing the laminae with sublaminar titanium cables of the upper end vertebrae. For fixation of the lower spine a dual-opening pedicle screw system is used. Using a holding forceps the distal rods are introduced and fixed into the side opening of the screws then secured by sublaminar wires. In addition both single rods are stabilized by a low profile cross link bar. This technique allows to correct pelvic obliquity and a stable anchorage of two screws reduces risk of postoperatively rotation or caudal rod slippage due to gravity forces.     

Photoreceptor topography in the duplex retina of the paddlefish (Polyodon spathula)

Retinal whole-mount preparations from the eyes of the North American paddlefish, Polyodon spathula, were examined with a combination of bright field and differential interference contrast microscopy. The entire retina was mapped and population counts of rod and cone photoreceptors were made at regular intervals throughout the retina. The retina is dominated by rods, but a significant percentage (ca. 38%) of the photoreceptors are cones. Mean cone packing density for the entire retina is 6,402+/-1,216 cones/mm2. There is a small (16%) but statistically significant difference between cone packing density in the dorsal retina (6,674+/-1,168 cones/mm2) and the ventral retina (5,745+/-1,076 cones/mm2). There is no region of unusually high cone concentration that might be construed as a fovea or a visual streak. Mean rod packing density for the entire retina is 10,271+/-1,205 rods/mm2. Except in the far periphery, where rods are less numerous, the density of rods is fairly uniform throughout the retina. The data are discussed with regard to paddlefish habitat and behavior.     

Ultrastructure of the in situ adherence of Mobiluncus to vaginal epithelial cells

From patients with bacterial vaginosis motile, anaerobic, comma-shaped bacteria can be isolated, which have recently been placed into the new genus Mobiluncus. In this study, electron microscopy was used to examine the in situ adherence of these motile curved rods to detached epithelial cells (comma cells) in vaginal fluid from two patients with bacterial vaginosis. Thin sections showed that the curved rods attached both directly to the epithelial cell surface and at various distances from it. It is concluded that after initial attachment these motile bacteria can grow at the epithelial cell surface in sessile microcolonies. Ruthenium red staining demonstrated a coating of precipitated glycocalyx material both on the surface of the curved rods and on their flagella. This may indicate that in situ the adherent curved rods were enclosed in a very hydrated matrix of exopolysaccharides. Conspicuous was the ability of the curved rods to attach to the epithelial cell surface via their cell tips. However, in situ no specialized bacteria cell surface structures were seen that might explain this polar attachment. Electron microscopy of pure cultures demonstrated that both Mobiluncus curtisii subsp. curtisii and Mobiluncus mulieris can produce a glycocalyx in vitro.     

A Kinetic Model for the Energy Transfer in Phycobilisomes

A kinetic model for the energy transfer in phycobilisome (PBS) rods of Synechococcus 6301 is presented, based on a set of experimental parameters from picosecond studies. It is shown that the enormous complexity of the kinetic system formed by 400-500 chromophores can be greatly simplified by using symmetry arguments. According to the model the transfer along the phycocyanin rods has to be taken into account in both directions, i.e., back and forth along the rods. The corresponding forward rate constants for single step energy transfer between trimeric disks are predicted to be 100-300 ns^-1. The model that best fits the experimental data is an asymmetric random walk along the rods with overall exciton kinetics that is essentially trap-limited. The transfer process from the sensitizing to the fluorescing C-PC phycocyanin chromophores (τ ≈ 10 ps) is localized in the hexamers. The transfer from the innermost phycocyanin trimer to the core is calculated to be in the range 36-44 ns^-1. These parameters lead to calculated overall rod-core transfer times of 102 and 124 ps for rods containing three and four hexamers, respectively. The model calculations confirm the previously suggested hypothesis that the energy transfer from the rods to the core is essentially described by one dominant exponential function. Extension of the model to heterogeneous PBS rods, i.e., PBS containing also phycoerythrin, is straightforward.     

A comparative study of the rod and coccoid forms of Campylobacter jejuni ATCC 29428

Coccoid forms in cultures of a strain of the enteric pathogen Campylobacter jejuni were investigated. A culture containing 100% coccoid forms was non-viable. Coccoid forms had a lesser content of cytoplasmic components and nucleic acids than rods of C. jejuni. During the conversion to coccoid forms nucleotides leaked from the cells. The results of treatments with ionic and non-ionic detergents, and lysozyme and ethylenediaminetetraacetic acid indicated a changed cell wall in coccoid forms compared with rods. Using rate-zonal centrifugation coccoid forms were found to be less dense than rods. The results of this study indicate that the coccoid form of C. jejuni ATCC 29428 is a degenerate cell form which is undergoing cellular degradation.     

A comparative study of the rod and coccoid forms of Campylobacter jejuni ATCC 29428

Coccoid forms in cultures of a strain of the enteric pathogen Campylobacter jejuni were investigated. A culture containing 100% coccoid forms was non-viable. Coccoid forms had a lesser content of cytoplasmic components and nucleic acids than rods of C. jejuni. During the conversion to coccoid forms nucleotides leaked from the cells. The results of treatments with ionic and non-ionic detergents, and lysozyme and ethylenediaminetetraacetic acid indicated a changed cell wall in coccoid forms compared with rods. Using rate-zonal centrifugation coccoid forms were found to be less dense than rods. The results of this study indicate that the coccoid form of C. jejuni ATCC 29428 is a degenerate cell form which is undergoing cellular degradation.     

Three-dimensional structure of the frozen-hydrated flagellar filament. The left-handed filament of Salmonella typhimurium

Electron micrographs of frozen-hydrated preparations of flagellar filaments of Salmonella typhimurium were used to obtain a three-dimensional reconstruction of the structure. The filaments were obtained from the mutant SJW1660, which produces straight, left-handed filaments. The subunits in this filament are thought to be all in the L-state. The structure consists of a set of 11 longitudinal segmented rods of density that lie at a radius of 70 A. The outermost feature of the filament is a set of knobs of density that project outward from the rods. The interior of the filaments consists of arms that extend inward radially from the segmented rods. The 11 segmented rods and their interconnections are noteworthy because current theories regarding filament structure involve switching of subunits between the L and R states co-operatively along the directions of the rods.