2,3-Epoxybrassinosteroids are intermediates in the biosynthesis of castasterone in seedlings of Secale cereale

The involvement of the 2,3-epoxybrassinosteroids secasterone and 2,3-diepisecasterone in the biosynthesis of castasterone has been demonstrated in seedlings of Secale cereale by LC-ESI-MS. Deuterated secasterone, upon administration to rye seedlings, was incorporated into castasterone and its 2beta- and 3beta-epimers. Administration of deuterated 2,3-diepisecasterone resulted in castasterone and 2-epicastasterone. A biosynthetic subpathway from typhasterol/teasterone via 2,3-epoxybrassinosteroid intermediates to castasterone is discussed.     

Influence of Fabrication Methods of Gold and Silver Layers on Surface Plasmon Polaritons Propagation Length

We present an experimental study of surface plasmon polaritons (SPPs) propagation length (L_SPP) on polycrystalline metal (gold and silver) films, fabricated by evaporation and sputtering techniques on glass substrates. For the excitation of SPPs, polymer grids on the sample surface are used. The SPPs are excited by a He-Ne (633 nm) and the L_SPP are measured by grating-coupling method and the leakage radiation microscopy. Dependence of L_SPP on the film thickness is also investigated. The longer L_SPP is observed with evaporation technique in comparison to the sputtering technique for the silver films. On the other hand, sputtering technique provides longer L_SPP for the gold films. Additionally, atomically flat crystalline gold flakes are also considered for the SPPs evaluation. The L_SPP estimation on these flakes is carried out for light wavelength of 633 and 800 nm.

     

A new species of the genus Polyrhanis Rivalier, 1963 (Coleoptera: Cicindelidae) from Papua (New Guinea,Indonesia)

A new tiger beetles species, Polyrhanis dabraensis sp. nov., is described from Dabra (Foja mountains region, Papua, New Guinea, Indonesia). Its elytral markings are similar to those of Polyrhanis funerata and P. barbata, but it is much smaller and its anteapical spot is more expanded on the disc and is connected with the apical lunule. The aedeagus has a thin straight hook (spur) directed perpendicularly on the dorsal side, like that of P. io, P. innocentior, P. excisilabris, P. olthofi, and P. vannideki. It is easily recognized by its distinctive elytral markings and small body size.     

Are combined analyses better than single gene phylogenies? A case study using SSU rDNA and rbcL sequence comparisons in the Zygnematophyceae (Streptophyta)

Although the combination of different genes in phylogenetic analyses is a promising approach, the methodology is not well established and analyses often suffer from inadequate, noncongruent taxon sampling, long-branch attraction, or conflicting evolutionary models of the genes analyzed. Conflicts or congruence between multigene and single-gene phylogenies, as well as the assumed superiority of the multigene approach, are often difficult to assess solely because of incongruent taxon sampling. In the present study, a data set of 43 nuclear-encoded SSU rDNA and plastid-encoded rbcL gene sequences was generated from the same strains of conjugating green algae (Zygnematophyceae, Streptophyta). Phylogenetic analyses used the genes individually and in combination, either as concatenated sequences or with the log-likelihood summation method. Single-gene analyses, although mostly congruent, revealed some conflicting nodes and showed different patterns of statistical support. Combined analyses confidently resolved the conflicts between the single-gene analyses, enhanced phylogenetic resolution, and were better supported by morphological information. Long-branch taxa were not the same for the two genes analyzed, and, thus, their effect on phylogenetic resolution was minimized in the combined analyses.     

The Rac/Cdc42 guanine nucleotide exchange factor beta1Pix enhances mastoparan-activated Gi-dependent pathway in mast cells

Carbachol stimulates granule exocytosis, phospholipase C (PLC), and phospholipase D (PLD) in RBL-2H3hm1 mast cells by a mechanism that involves Galphaq. However, mastoparan stimulates the same responses through Gi protein. Both Gi and Galphaq pathways are suppressed by Clostridium difficile toxin B, suggesting that Rac and Cdc42 small GTPases are also involved. Over-expression of beta1Pix, a guanine nucleotide exchange factor for Rac and Cdc42, enhances mastoparan-but not carbachol-induced hexosaminidase secretion and PLC and PLD activation. Furthermore, cells expressing beta1Pix exhibit elevated levels of mastoparan-stimulated IP3 production. Taken together, these findings implicate beta1Pix in regulating hexoasaminidase secretion and IP3 production in early stage upon mastoparan stimulation.     

Of proteins and RNA: The RNase P/MRP family

Nuclear ribonuclease (RNase) P is a ubiquitous essential ribonucleoprotein complex, one of only two known RNA-based enzymes found in all three domains of life. The RNA component is the catalytic moiety of RNases P across all phylogenetic domains; it contains a well-conserved core, whereas peripheral structural elements are diverse. RNA components of eukaryotic RNases P tend to be less complex than their bacterial counterparts, a simplification that is accompanied by a dramatic reduction of their catalytic ability in the absence of protein. The size and complexity of the protein moieties increase dramatically from bacterial to archaeal to eukaryotic enzymes, apparently reflecting the delegation of some structural functions from RNA to proteins and, perhaps, in response to the increased complexity of the cellular environment in the more evolutionarily advanced organisms; the reasons for the increased dependence on proteins are not clear. We review current information on RNase P and the closely related universal eukaryotic enzyme RNase MRP, focusing on their functions and structural organization.     

Expression of raf serine/threonine protein kinases in the cell bodies of primary sensory neurons of the adult rat

We have used immunocytochemistry to examine the distribution of raf protein kinases in sensory neurons of the adult rat. In lumbar and trigeminal sensory ganglia, cells of all size ranges appeared to be raf immunoreactive and this was confirmed by double labeling using subpopulation specific markers. Almost all cells labeled with Griffonia simplicifolia IB4 (a small cell marker) or immunostained by using a large cell marker (RT97) showed raf immunoreactivity. These two markers label cells known to differ in their expression of neurotrophin receptors (trk). Thus raf kinases are not confined to cells expressing only certain trk subtypes. In the dorsal horn of the spinal cord, raf immunoreactivity was present in scattered neurons. However, sensory axons identified by IB4 histochemistry were devoid of raf immunostaining. Lectin-labeled nerve fibers in the cornea, lower lip and glans penis were also not immunoreactive. Ligation of the sciatic nerve did not produce any accumulation of raf immunoreactivity, confirming that raf kinases are not axonally transported to the peripheral processes of sensory neurons. Surgical dissection of the sciatic nerve caused the normal homogeneous cytoplasmic raf immunoreactivity to be replaced in some cells by a staining concentrated predominantly under the plasma membrane. One possibility is that this represents activation of raf in these cells. Received: 2 October 1995 / Accepted: 4 March 1996     

Orientational Ordering of Carotenoids in Myelin Membranes Resolved by Polarized Raman Microspectroscopy

We study orientational ordering of membrane compounds in the myelinated nerve fiber by means of polarized Raman microspectroscopy. The theory of orientational distribution functions was adapted to live-cell measurements. The obtained orientational distribution functions of carotenoids and lipid acyl chain clearly indicated a predominantly radial-like orientation in membranes of the myelin. Two-dimensional Raman images, made under optimal polarization of incident laser beam, corroborated the proposed carotenoid orientation within the bilayer. Experimental data suggested the tilted orientation of both carotenoid polyenic and lipid acyl chains. The values of maximum tilt angles were similar, with possible implication of carotenoid-induced ordering effect on lipid acyl chains, and hence change of myelin membrane properties. This study stages carotenoids of the nerve as possible mediators of excitation and leverages underlying activity-dependent membrane reordering.