Correlation between arrested secondary plasmodesmal development and onset of accelerated leaf senescence in yeast acid invertase transgenic tobacco plants

Mature leaves of a transgenic tobacco plant ( Nicotiana tabacum L var. Samsun, line A41-10) that constitutively express a yeast-derived acid invertase gene develop symptoms which are characterized by the presence of greenish-yellow and green sectors in the same leaf, and onset of early, leaf senescence. Previous studies indicated that invertase activity was two- to threefold higher in the greenish-yellow sectors than in the green sectors. Our structural analyses revealed that development of secondary plasmodesmata, via modification of existing primary plasmodesmata, between mesophyll cells was inhibited severely in the greenish-yellow sectors, but only marginally in the green sectors. In contrast, the structure and function of primary plasmodesmata in the same symptomatic sectors remained unaltered as determined by structural and dye coupling studies. It is hypothesized that secondary plasmodesmata differ from primary plasmodesmata in having special abilities to traffic information molecules to coordinate leaf development and physiological function(s). Arrest of secondary plasmodesmal development by high invertase activity in the transgenic tobacco leaf may have prevented this type of trafficking and hence resulted in early leaf senescence. The results also indicate that the yeast acid invertase-expressing tobacco may provide an effective experimental system for the molecular characterization of cellular mechanisms that regulate the development, function, and possible turnover of secondary plasmodesmata.     

Natural lignin modulators improve bagasse saccharification of sugarcane and energy cane in field trials

The burgeoning cellulosic ethanol industry necessitates advancements in enzymatic saccharification, effective pretreatments for lignin removal, and the cultivation of crops more amenable to saccharification. Studies have demonstrated that natural inhibitors of lignin biosynthesis can enhance the saccharification of lignocellulose, even in tissues generated several months post-treatment. In this study, we applied daidzin (a competitive inhibitor of coniferaldehyde dehydrogenase), piperonylic acid (a quasi-irreversible inhibitor of cinnamate 4-hydroxylase), and methylenedioxy cinnamic acid (a competitive inhibitor of 4-coenzyme A ligase) to 60-day-old crops of two conventional Brazilian sugarcane cultivars and two energy cane clones, bred specifically for enhanced biomass production. The resultant biomasses were evaluated for lignin content and enzymatic saccharification efficiency without additional lignin-removal pretreatments. The treatments amplified the production of fermentable sugars in both the sugarcane cultivars and energy cane clones. The most successful results softened the most recalcitrant lignocellulose to the level of the least recalcitrant of the biomasses tested. Interestingly, the softest material became even more susceptible to saccharification.     

Utilization of metabolic scope in relation to feeding and activity by individual and grouped zebrafish, Brachydanio rerio (Hamilton-Buchanan)

Metabolic scope and its utilization in relation to feeding and activity were measured in individual and grouped zebrafish (weight range, 430–551 mg) at 24° C by respirometry. Mean maximum metabolic rate, induced by swimming to exhaustion, R_max(i), was 1223 (s.d. , 157) mg O₂, kg^?1 h^?1 for individuals. Standard metabolic rate, R_s. was 364 mg O₂ kg^?1 h^?1, as estimated by extrapolating to zero activity from measurements of unfed, spontaneously active individuals. Mean routine metabolic rate, R_rout, of individuals was 421 (s.d. , 58) mg O₂, kg_-1 h_-1. The mean voluntary maximum metabolic rate, R_max(v), following transfer of minimally exercised fish to the respirometer, was 1110 (s.d. , 83) mg O₂ kg ^?1 h^?1 for groups of six fish, and was not significantly different from the value measured for individuals, 1066 (s.d. , 122) mg O₂, kg^?1 h^?1. Grouped fish acclimated to the respirometer more slowly than individual fish and exhibited significantly higher R_rout, apparently a result of greater social interaction and activity in groups. Mean R_rout for groups was 560 (s.d. , 78) mg O₂, kg^?1 h^?1. While groups of zebrafish fed a ration of 5% wet body weight day^?1 exhibited consistently higher metabolic rates than fish fed rations of 2.5% wet body weight day^?1 the high ration group still used only a maximum of 77% of the metabolic scope. Zebrafish of the size studied do not appear to demonstrate a high degree of conflict in utilization of metabolic scope by different respiratory components. The metabolic rates measured for zebrafish are among the highest yet measured for fish of similar size and at similar temperatures.     

THE FINE STRUCTURE OF TWO PHOTOSYNTHETIC SPECIES OF DINOPHYSIS (DINOPHYSIALES,DINOPHYCEAE)1

Two closely related, photosynthetic species belonging to the genus Dinophysis were examined, D. acuminata Claparède et Lachmann and D. fortii Pavillard. Typical dinoflagellate features include the amphiesmal covering enclosing the cells and the structure of the nucleus and mitochondria. Many other characteristics seem to be specific to the order Dinophysiales. Many rhabdosomes are present, and complex mucocysts are found beneath the amphiesma. The thecal pores are unusual with the base of the pore occluded by a thin disc that is continuous with the main amphiesmal plate. The structure of the apical pore is also distinctive. Chloroplasts are grouped together in chromatospheres, enclosed by a double membrane, and contain paired thylakoids with electron dense contents in the lumen. The two pusules are extensive, each branching off the flagellar canal, and consisting of a large antechamber and a number of convoluted sacs. The entrance of each antechamber, and site of an emerging flagellum, is surrounded by a striated fibrous collar. Near the flagellar pore is a prominent microtubular/microbody complex which penetrates deep into the cell cytoplasm. Consideration is given to taxonomic position of the Dinophysiales and also to the nature and origins of the chloroplasts.     

Absence of plasma membrane H+-ATPase in plasmodesmata located in pit-fields of the young reactive pulvinus ofMimosa pudica L.

Summary Immunocytochemical techniques were employed to study the spatial distribution of the plasma membrane H⁺-ATPase within various cell types of the young reactive primary pulvinus ofMimosa pudica L. These cells were interconnected by large numbers of plasmodesmata, being concentrated within pit-fields. Although we could routinely detect evidence of the H⁺-ATPase along the plasma membrane, immunolabelling was rarely, if ever, observed along the plasma membranes of the plasmodesmata. This finding is discussed with respect to the likely specialized supramolecular structure of the plasmodesma.Abbreviations SEL size exclusion limit of plasmodesmata     

Macrocylic thioether-esters and thioether-thioesters and their palladium, platinum and silver complexes

Preparations by the high dilution method are reported for seven macrocyclic thioether-esters and thioether-thioesters (L1–;L7). Yields in these reactions between thiodiglycolyl dichloride and appropriate ,ω-diols or dithiols range from 10 to 51%. The compounds are characterized by ¹H and ¹³C NMR, IR and high resolution mass spectroscopy. They react with salts of Pd(II), Pt(II) and Ag(I) to form complexes of which MX₂·L2, (M = Pt, X = Cl; M = Pd, X = Cl, Br, I, SCN), [Pd(L2)₂][CF₃SO₃]₂·H₂O and [Ag(L5)₂][CF₃SO₃]·C₂H₅OH have been isolated and characterized by elemental analysis, IR and NMR spectroscopy. NMR spectra indicate reversible dissociation of the ligand occurs in dimethyl sulfoxide solvent for PdCl₂·L2 but not for the Pt analogue. For PtCl₂·L2, spectra indicate that the ligand is undergoing a conformational ‘wag’ about its pair of equivalent sulfurs. These remain bound to the metal while the unique sulfur moves from the apical position of the coordination sphere to a non-coordinated situation. Simultaneously, inversions at the bound sulfurs are occurring.     

An easy method for the removal of Epon resin from semi-thin sections. Application of the avidin-biotin technique

Summary A simple procedure is described for removing Epon resin from semi-thin 1 m sections, which permits excellent postembedding immunohistochemical staining (avidin-biotin complex technique). The procedure was developed for the detection of growth hormone and prolactin in bovine adenohypophysis fixed with 2% paraformaldehyde and 0.5% glutaraldehyde in 0.1 m sodium cacodylate buffer pH 7.4–7.6. The results indicate that the removal of the epoxy embedding medium prior to the application of the immunohistochemical reagents was essential for the successful localization of the antigenic determinants of the two hormones. The immunocytochemical reactivity was obtained only after treating the sections with a solution of potassium hydroxide in a mixture of absolute methyl alcohol and propylene oxide (Maxwell's solution). An enhanced immunoreactivity was obtained when this treatment was followed by an additional treatment with either 4% hydrogen peroxide or a saturated aqueous solution of sodium metaperiodate. Because of the easy preparation of the Epon removal solution and the good structural preservation without damage to the antigenic determinants, Maxwell's solution is suggested as a good etching agent which can be used in immunohistochemical studies on semi-thin sections with excellent results.     

Inequalities in income and long-term disability in Spain: analysis of recent hypotheses using cross sectional study based on individual data.

OBJECTIVE: To compare the relation between inequalities in long-term disability and income in the 17 regions of Spain. DESIGN: Data were taken from the survey on impairments, disabilities, and handicaps that was carried out in Spain in 1986. For each region the inequality in long-term disability associated with income was calculated as the odds ratio associated with reducing monthly household income by 10,000 pesetas (about Ponds 50) (estimate of effect of inequality of income) and the odds ratio for the inequality in long-term disability between those at the bottom and those at the top of the income hierarchy (relative index of inequality). MAIN OUTCOME MEASURE: Prevalence of long-term disability. RESULTS: Five of the eight regions where lowering income had a greater effect on long-term disability were among those with the lowest income per head, while six of the remaining nine regions where the effect was smaller were among those with the highest income per head. Three regions with the highest estimate of relative index of inequality had the highest estimate of effect, and another three regions with the lowest estimate of relative index of inequality had the lowest estimate of effect. In contrast, the relative position of the remaining 11 regions varied from one measure to another. CONCLUSIONS: These results support the theory that additional increments in material wellbeing have a negligible effect on health in countries with high socioeconomic development. However, inequality in income distribution did not determine inequality in health between those at the bottom and those at the top of the income hierarchy in many Spanish regions.     

Adrenomedullary Secretion of DOPA, Catecholamines, Catechol Metabolites, and Neuropeptides

Abstract: Catecholamines and their metabolites have been proposed as markers of sympathetic nervous system stimulation. However, the adrenal medulla is a rich source of catecholamines and catecholamine metabolites and may play a significant role in plasma levels of these compounds. In addition to adrenal catecholamine metabolite efflux, the role of the catecholamine precursor 3,4-dihydroxyphenylalanine (DOPA) has not been fully evaluated. The simultaneous effluxes of catecholamines, metabolites, DOPA, and neuropeptides were measured in perfusates from isolated dog adrenals. The relative abundance of compounds detected consistently during unstimulated conditions was epinephrine ≫ norepinephrine > 3,4-dihydroxyphenylglycol > metanephrine > normetanephrine > dopamine > 3,4-dihydroxyphenylacetic acid > 3-methoxy-4-hydroxyphenylglycol ≥ DOPA ≫ [Met]enkephalin ≫ neuropeptide Y. Effluxes of analytes were not affected by cocaine and the ratios of catecholamines to metabolites increased dramatically with carbachol stimulation, consistent with negligible reuptake into adrenal cells. Thus, most of the 3,4-dihydroxyphenylglycol is expected to be derived from epinephrine and norepinephrine subsequent to translocation from chromaffin vesicles into the cytosol. The efflux of DOPA increased dramatically during stimulation with 30 µ M carbachol in a calcium-dependent manner. Efflux of DOPA during the initial stabilization period of the perfusion preparation declined exponentially, in parallel with the effluxes of the catecholamines and neuropeptides but not with metabolites. Evoked release of DOPA was Ca²⁺-dependent. These data suggest that DOPA can be stored and released exocytotically from chromaffin granules.