Uptake, transport and metabolism of cytokinin in moss protonema

Uptake, transport and metabolism of cytokinin in the protonemaof Funaria hygrometrica were studied using labelled kinetin(6-furfurylamino [8-¹⁴C]-purine). All cells of the protonema,chloronema and caulonema, were able to take up kinetin, whichwas carried in the symplastic transport system from cell tocell. Radioactivity was especially accumulated in growing cellsof the protonema. Kinetin was metabolized immediately afteruptake. While only very little kinetin (less than 1%) remainedas free kinetin and one part was immobilized in chromatographicseparation [e.g. attached to proteins and incorporated intonucleic acids (17)], most of the remaining kinetin was metabolizedto adenine derivatives. Exogenously supplied adenosine changedthe metabolism of kinetin. In the caulonema, adenosine reducedthe turnover of kinetin to other adenine derivatives and enhancedthe content of labelling in the start fraction. Thus adenosinecan stimulate cytokinin-dependent bud formation in moss protonema. (Received November 24, 1977; )     

Marabou Storks Wash Dung Beetles

Marabou Storks in their natural environment were observed to practise an insightful method of food amelioration.     

Structure and function of lamellar bodies, lipid-protein complexes involved in storage and secretion of cellular lipids.

This review article attempts to present an overview of the occurrence and function of lipid storage and secretory organelles: the lamellar bodies. Morphologically these organelles vary considerably in size (100 nm to 2400 nm); they are surrounded by a membrane and contain multilamellar lipid membranes. Lamellar bodies may also contain apolipoproteins and lytic enzymes and have an acidic pH, which confers on them a lysosomal character. Under normal physiological conditions, the main function of lamellar bodies is the supply of extracellular domains with specialized lipid components related to a specialized function. The lamellar bodies of the lung epithelium are best investigated in their functional and structural features and are the storage form of the lung surfactant. They provide a monomolecular lipid film of dipalmitoyl phosphatidylcholine (DPPC) on the surface of lung alveoli to lower surface tension necessary for optimal gas exchange and a hydrophobic protective lining against environmental influences. Additional cells of the respiratory system such as the mucosa of the human nose and the bronchi contain lamellar bodies. Lamellar bodies are also found in the gastrointestinal tract, in tongue papillae, oral epithelium, and mucosa cells of the stomach. The major phospholipid of lamellar bodies in mucosa cells of the stomach is DPPC, providing a hydrophobic protective lipid film against the tissue-damaging activities of gastric juice. The hydrophobic water-protective barrier of the skin, which consists mainly of neutral lipids, however, also originates from lamellar bodies secreted by epithelial cells. Lamellar bodies, mainly consisting of DPPC, also occur in mesodermal cell layers of sliding surfaces to provide the lubrication of joints, of the peritoneum, pericardium, and pleural mesothelium. In certain pathological conditions, such as atherosclerosis, Niemann-Pick disease, lecithin:cholesterol acyltransferase (LCAT) deficiency, cholestasis, degeneration of nerves and brain, and regeneration of nerves and wound healing, lipid-containing lamellar bodies have been observed in various cells, the function of which still remains to be elucidated. In early and late lesions of atherosclerotic plaques, lamellar bodies, consisting of unesterified cholesterol and phospholipids, are associated with the extracellular matrix of the intima. During regression of fatty streaks, lamellar bodies are seen intracellularly in macrophages and smooth muscle cells. Inherited metabolic disorders, such as Niemann-Pick disease type I and type II, result in the excessive accumulation of lamellar body-containing cells, for example in bone marrow, spleen, and lymphoid tissue. Type I is a deficiency in sphingomyelinase and type II is a defect in intracellular trafficking of lipoprotein-derived cholesterol.(ABSTRACT TRUNCATED AT 400 WORDS)     

Base-pair probability profiles of RNA secondary structures

Dynamic programming algorithms are able to predict optimal andsuboptimal secondary structures of RNA. These suboptimal oralternative secondary structures are important for the biologicalfunction of RNA. The distribution of secondary structures presentin solution is governed by the thermodynamic equilibrium betweenthe different structures. An algorithm is presented which approximatesthe total partition function by a Boltzmann–weighted summationof optimal and suboptimal secondary structures at several temperatures.A clear representation of the equilibrium distribution of secondarystructures is derived from a two-dimensional bonding matrixwith base–pairing probability as the third dimension.The temperature dependence of the equilibrium distribution givesthe denaturation behavior of the nucleic acid, which may becompared to experimental optical denaturation curves after correctionfor the hypochromicities of the different base-pairs. Similarly,temperature-induced mobility changes detected in temperature-gradientgel electrophoresis of nucleic acids may be interpreted on thebasis of the temperature dependence of the equilibrium distribution.Results are illustrated for natural circular and synthetic linearpotato spindle tuber viroid RNA respectively, and are comparedto experimental data.     

Deoxyribose conformation in [d(GTATATAC)]2: evaluation of sugar pucker by simulation of double-quantum-filtered COSY cross-peaks

Exchangeable and nonexchangeable proton and phosphorus resonances (11.75 T) of [d(GTATATAC)]2 in aqueous solution were assigned by using proton two-dimensional nuclear Overhauser effect (2D NOE) spectra, homonuclear proton double-quantum-filtered COSY (2QF-COSY) spectra, proton spin-lattice relaxation time measurements, and 31P1H heteronuclear shift correlation spectra. Due to the large line widths, it was not possible to directly extract vicinal proton coupling constant values from any spectrum including ECOSY or 2QF-COSY. However, comparison of quantitative 2QF-COSY spectral simulations with experimental spectra enabled elucidation of coupling constants. The scope and limitations of this approach were explored by computation and by use of experimental data. It was found that proton line widths exhibit some variability from one residue to the next as well as from one proton to the next within a residue and the exact line width is critical to accurate evaluation of coupling constants. Experimental 2QF-COSY spectra were not consistent with a rigid deoxyribose conformation for any of the nucleotide residues. A classical two-state model, with rapid jumps between C2'-endo (pseudorotation angle P = 162 degrees) and C3'-endo (P = 9 degrees) conformations, was able to account for the spectral characteristics of terminal residue sugars: 60% C2'-endo and 40% C3'-endo. However, the 2QF-COSY cross-peaks from the -TATATA- core could be simulated only if the classical two-state model was altered such that the dominant conformer had a pseudorotation angle at 144 degrees instead of 162 degrees. In this case, the major conformer amounted to 80-85%. Alternatively, the spectral data were consistent with a three-state model in which C2'-endo and C3'-endo conformations had the largest and smallest populations, respectively, but a third conformer corresponding to C1'-exo (P = 126 degrees) was present, consistent with recent molecular dynamics calculations. This alternative yielded populations of 50% (P = 162 degrees), 35% (P = 126 degrees), and 15% (P = 9 degrees) for the -TATATA- sugars. The spectral results indicate little variation of sugar pucker between T and A. Small differences in cross-peak component intensities and characteristic spectral distortions, however, do suggest some unquantified variation. 31P1H heteronuclear chemical shift correlation spectra manifested alternating chemical shifts and coupling constants suggestive of phosphodiester backbone conformational differences between TA and AT junctions.     

Production of 3-acetoxyscirpene-4,15-diol from anguidine (4,15-diacetoxyscirpene-3-ol) by Fusarium oxysporum f.sp. vasinfectum.

Growing cells of Fusarium oxysporum f.sp. vasinfectum (ATCC 7808) formed 3-acetoxyscirpene-4,15-diol from anguidine (4,15-diacetoxyscirpene-3-ol) by way of the intermediates triacetoxyscirpene, 3,4-diacetoxyscirpene-15-ol and 3,15-diacetoxyscirpene-4-ol. The new 3-acetoxy analog was found to be less active than anguidine and the other monoacetoxy derivatives when tested against a series of fungal strains and against HeLa cells in vitro.     

The interaction of RNA polymerase and lac repressor with the lac control region.

We have examined the interactions of lac repressor and RNA polymerase with the DNA of the lac control region, using a method for direct visualization of the regions of DNA protected by proteins from DNAase attack. The repressor protects the operator essentially as reported by Gilbert and Maxam (1) with some small modifications. However, the evidence reported here concerning the binding of RNA polymerase to the DNA of the promoter mutant UV5 indicates that : 1) the RNA polymerase molecule binds asymmetrically to the promoter DNA, 2) RNA polymerase protects DNA sequences to within a few bases of the CAP binding site, suggesting direct interaction between polymerase and the CAP protein at this site, 3) RNA polymerase still binds to the promoter when repressor is bound to the operator, but fails to form the same extensive complex.