The tRNATyr multigene family of Nicotiana rustica: genome organization,sequence analyses and expression in vitro

Tobacco tRNA^Tyr genes are mainly organized as a dispersed multigene family as shown by hybridization with a tRNA^Tyr-specific probe to Southern blots of Eco RI-digested DNA. A Nicotiana genomic library was prepared by Eco RI digestion of nuclear DNA, ligation of the fragments into the vector gtWES·B and in vitro packaging. The phage library was screened with a 5-labelled synthetic oligonucleotide complementary to nucleotides 18 to 37 of cytoplasmic tobacco tRNA^Tyr. Eleven hybridizing Eco RI fragments ranging in size from 1.7 to 7.5 kb were isolated from recombinant lambda phage and subcloned into pUC19 plasmid. Four of the sequenced tRNA^Tyr genes code for the known tobacco tRNA₁ ^Tyr (GA) and seven code for tRNA₂ ^Tyr (GA). The two tRNA species differ in one nucleotide pair at the basis of the TC stem. Only one tRNA^Tyr gene (pNtY5) contains a point mutation (T54A54). Comparison of the intervening sequences reveals that they differ considerably in length and sequence. Maturation of intron-containing pre-tRNAs was studied in HeLa and wheat germ extracts. All pre-tRNAs^Tyr-with one exception-are processed and spliced in both extracts. The tRNA^Tyr gene encoded by pNtY5 is transcribed efficiently in HeLa extract but processing of the pre-tRNA is impaired.     

The spectral input systems of hymenopteran insects and their receptor-based colour vision

Summary Spectral sensitivity functions S() of single photoreceptor cells in 43 different hymenopteran species were measured intracellularly with the fast spectral scan method. The distribution of maximal sensitivity values (_max) shows 3 major peaks at 340 nm, 430 nm and 535 nm and a small peak at 600 nm. Predictions about the colour vision systems of the different hymenopteran species are derived from the spectral sensitivities by application of a receptor model of colour vision and a model of two colour opponent channels. Most of the species have a trichromatic colour vision system. Although the S() functions are quite similar, the predicted colour discriminability curves differ in their relative height of best discriminability in the UV-blue or bluegreen area of the spectrum, indicating that relatively small differences in the S() functions may have considerable effects on colour discriminability. Four of the hymenopteran insects tested contain an additional R-receptor with maximal sensitivity around 600 nm. The R-receptor of the solitary bee Callonychium petuniae is based on a pigment (P596) with a long _max, whereas in the sawfly Tenthredo campestris the G-receptor appears to act as filter to a pigment (P570), shifting its _max value to a longer wavelength and narrowing its bandwidth. Evolutionary and life history constraints (e.g. phylogenetic relatedness, social or solitary life, general or specialized feeding behaviour) appear to have no effect on the S() functions. The only effect is found in UV receptors, for which _max values at longer wavelengths are found in bees flying predominantly within the forest.     

Immunocytochemical identification of neural elements in the central nervous systems of a snail,some insects,a fish,and a mammal with an antiserum to the molluscan cardio-excitatory tetrapeptide FMRF-amide

Summary The choriocapillaris is the fenestrated capillary network that supplies a large portion of the nutrients required by the retinal pigment epithelium, photoreceptor cells, and other cells of the outer neural retina. The permeability of these capillaries was investigated in the rat by the use of ferritin (mol. wt. approx. 480,000; mol. diam. 110Å) as a tracer. Ninety minutes after intravascular ferritin administration, a high concentration of tracer particles was distributed uniformly in the capillary lumina but few particles were present in Bruch's membrane, the multilayered basement membrane that separates the choriocapillary endothelium from the retinal pigment epithelium. The bulk of the tracer remained in the capillary lumina with a definite blockage seen at fenestral, channel, and vesicle diaphragms. These results indicate that the rat choriocapillary endothelium, unlike the fenestrated endothelia lining other capillary beds, constitutes an important barrier to the passage of ferritin and presumably of circulating native molecules of similar size.Supported by NIH grants EY 01889 and EY 07034 from the National Eye Institute and a grant-in-aid from Fight for Sight, Inc., of New York City     

Production ecology ofPhragmites communis 1. Relations of two ecotypes to the microclimate and nutrient conditions of habitat

The growth rate of stand biomass, the seasonal development of vertical stand structure and accumulation of mineral nutrients were compared in twoPhrogmites ecotypes; the stands occur in two different biotopes, littoral and limosal, situated in the littoral of the Opatovický fishpond in the South Bohemian fishpond basin. Microclimatological data including incoming global radiation were recorded in both biotopes during three growing seasons. The differences in morphological, chemical and production characteristics of the two reed ecotypes were in good relation with the edaphic, hydrochemical and microclimatological characteristics of their biotopes. These differences are reflected in a higher leaf area index, denser stand, higher production parameters and a higher efficiency in the conversion of solar energy in the limosal reed ecotype as compared with the littoral population. The differences in annual production and in energy conversion have not changed within seven growing seasons.     

Morphological features of F1 generation inRosa hybrids 1. Hybrids of some species of the sect.Caninae withRosa rugosa

In the present paper morphological features of hybrids from crossing of four species ofRosa sect.Caninae (R. canina L.,R. zalana Wiesb.,R. rubiginosa L. andR. sherardii Davies) withR. rugosa Thumbg. (sect.Cinnamomeae) and their heredity are described. F₁ generation appears more or less uniform, certain morphological features are patroclinal, other ones are matroclinal and intermediary. The general appearance of these hybrids is intermediary; there seems to be no reason to consider them matroclinal.     

Changes in the content of endogenous auxins in apical buds ofchenopodium rubrum L. Induced with respect to the endogenous rhythm in capacity to flower

The content of endogenous auxins was examined in apical buds ofChenopodium rubrum plants induced by a photoperiodic cycle of 16h darkness and 8h light followed by a dark period of various duration so as to correspond with either maximal or minimal flowering response in the endogenous rhythm in capacity to flower initiated by the photoperiodic treatment. Apical buds of potentially generative plants contained less auxins than apical buds of plants which remained in the vegetative state. Apical buds from plants treated with kinetin (1. 10^-3 M) and therefore remaining in the vegetative state showed an auxin level comparable to that of untreated plants exhibiting minimal flowering response irrespective of the duration of the second dark period. Plants cultivated on a sucrose solution (0.6 M) during the second dark period became generative even at the normal minimum of flowering. The auxin content of the apical buds was low, similarly as in untreated plants induced for a period leading to maximal flowering response. On the other hand, apical buds from plants grown on sucrose solution during a dark period leading to the manifestation of maximal flowering response showed a relatively high auxin content comparable to that found in untreated plants which had obtained a more extended induction by three photoperiodic cycles. The results are discussed with respect to the possible role of endogenous auxins in the regulation of the changes in growth correlations occurring in the shoot apex during photoperiodic induction and in the expression of the competence to flower.     

Participation of exogenous DNA in the repair processes of meristematicVicia faba cells injured by monofunctional alkylating agens ethylmethane sulphonate

The effect of exogenous DNA of syngeneic origin on the course of reparation of meristematic cells ofVicia faba primary roots followed after treatment with monofunctional alkylating agent, ethyl methanesulphonate (EMS), was tested. Time course of alternations in mitotic activity of investigated cellular population and the dynamics of formation of postmetaphase chromosomal aberrations was evaluated. A reparation of damaged cells was significantly supported by syngeneic DNA; its application induced an increased incidence of cellular division already in the early intervals of the repair which was accompanied by concomitant decrease of microscopically detectable rupture in the chromosomes. The study performed on the localization of induced damages occurring in metaphase chromosomes pointed out an increased sensitivity of small chromosomes ofVicia faba to EMS. Similarly, a reparative action of syngeneic DNA was exhibited by significant decrease of aberrations frequency, predominantly in the same chromosomal group. Per cent representation of individual types, not affected by the action of syngeneic DNA, was established by detailed classification of induced aberrations. In both cases, isochromatide breaks were found of greatest predominance.     

Biofilm community structure and the associated drag penalties of a groomed fouling release ship hull coating

Grooming is a proactive method to keep a ship’s hull free of fouling. This approach uses a frequent and gentle wiping of the hull surface to prevent the recruitment of fouling organisms. A study was designed to compare the community composition and the drag associated with biofilms formed on a groomed and ungroomed fouling release coating. The groomed biofilms were dominated by members of the Gammaproteobacteria and Alphaproteobacteria as well the diatoms Navicula, Gomphonemopsis, Cocconeis, and Amphora. Ungroomed biofilms were characterized by Phyllobacteriaceae, Xenococcaceae, Rhodobacteraceae, and the pennate diatoms Cyclophora, Cocconeis, and Amphora. The drag forces associated with a groomed biofilm (0.75 ± 0.09 N) were significantly less than the ungroomed biofilm (1.09 ± 0.06 N). Knowledge gained from this study has helped the design of additional testing which will improve grooming tool design, minimizing the growth of biofilms and thus lowering the frictional drag forces associated with groomed surfaces.     

Characterization of the endolysosomal system in human chordoma cell lines: is there a role of lysosomes in chemoresistance of this rare bone tumor?

Chordoma is a rare tumor of the bone derived from remnants of the notochord with pronounced chemoresistance. A common feature of the notochord and chordoma cells is distinct vacuolization. Recently, the notochord vacuole was described as a lysosome-related organelle. Since lysosomes are considered as mediators of drug resistance in cancer, we were interested whether they may also play a role in chemoresistance of chordoma. We characterized the lysosomal compartment in chordoma cell lines by cytochemistry, electron microscopy (ELMI) and mutational analysis of genes essential for the physiology of lysosomes. Furthermore, we tested for the first time the cytotoxicity of chloroquine, which targets lysosomes, on chordoma. Cytochemical stainings clearly demonstrated a huge mass of lysosomes in chordoma cell lines with perinuclear accumulation. Also vacuoles in chordoma cells were positive for the lysosomal marker LAMP1 but showed no acidic pH. Genetic analysis detected no apparent mutation associated with known lysosomal pathologies suggesting that vacuolization and the huge lysosomal mass of chordoma cell lines is rather a relict of the notochord than a result of transformation. ELMI investigation of chordoma cells confirmed the presence of large vacuoles, lysosomes and autophagosomes with heterogeneous ultrastructure embedded in glycogen. Interestingly, chordoma cells seem to mobilize cellular glycogen stores via autophagy. Our first preclinical data suggested no therapeutically benefit of chloroquine for chordoma. Even though, chordoma cells are crammed with lysosomes which are according to their discoverer de Duve “cellular suicide bags”. Destabilizing these “suicide bags” might be a promising strategy for the treatment of chordoma.     

NMR metabolomic study of blood plasma in ischemic and ischemically preconditioned rats: an increased level of ketone bodies and decreased content of glycolytic products 24 h after global cerebral ischemia

Cardiac arrest is one of the leading causes of death among adults in older age. Understanding mechanisms how organism responds to ischemia at global level is essential for the prevention and ischemic patient’s treatment. In this study, we used a global cerebral ischemia induced by four-vessel occlusion as an established animal model for ischemic stroke to investigate metabolic changes after 24 h reperfusion, when transitions occur due to the onset of delayed neuronal death. We also focused on the endogenous phenomenon known as ischemic tolerance by the pre-ischemic treatment. The experiments were carried out on blood plasma samples as easily available and metabolically reflecting the overall changes in injured organism. Our results imply that disturbed glycolysis pathway, as a consequence of ischemic injury, leads to the increased level of ketone bodies (acetone, acetoacetate and β-hydroxybutyrate) along with increased utilization of triacylglycerols in plasma of ischemic and ischemically preconditioned rats. Complementary to, a decreased level of glycolytic intermediates (lactate, pyruvate, acetate) with increased level of glucose was found in ischemic and preconditioned animals. The protective effect of ischemic preconditioning on metabolome recovery was demonstrated by significantly increased level of creatine compared to ischemic, non-preconditioned rats. We also document that acetoacetate, pyruvate, lactate, and leucine have the best discriminatory power between ischemic and control plasma. Conclusively, our results provide evidence that NMR spectra analysis can identify specific group of metabolites present in plasma with the capability for discrimination between individual groups of animals. In addition, an excellent feasibility for the statistical discrimination among ischemic, preconditioned, and control rats can be applied regardless of native or deproteinated plasma and also regardless of noesy or cpmg NMR acquisition.