Growth Regulators Have Rapid Effects on Photosynthate Unloading from Seed Coats of Phaseolus vulgaris L

Of nine plant growth regulators (indoleacetic acid, 1-naphthalene acetic acid, gibberellic acid, giberellin 4/7, 6-benzylaminopurine, 6-furfurylaminopurine, abscisic acid, and 1-aminocyclopropane carboxylic acid) tested, only 6-benzylaminopurine and abscisic acid affected ¹⁴C-photosynthate unloading from excised seed coats of Phaseolus vulgaris L. Unloading, in the presence of KCl, was stimulated by 25 to 40%. Stimulation occurred immediately for 6-benzylaminopurine and for abscisic acid within 10 to 12 minutes of application.     

Dipyridamole-insensitive nucleoside transport in mutant murine T lymphoma cells

From a mutagenized population of S49 murine T lymphoma cells, a mutant cell line, JPA4, was selected that expressed an altered nucleoside transport capability. JPA4 cells transported low concentrations of purine nucleosides and uridine more rapidly than the parental S49 cell line. The transport of these nucleosides by mutant cells was insensitive to inhibition by either dipyridamole (DPA) or 4-nitrobenzylthioinosine (NBMPR), two potent inhibitors of nucleoside transport in mammalian cells. Kinetic analyses revealed that the apparent Km values for the transport of uridine, adenosine, and inosine were 3-4-fold lower in JPA4 cells compared to wild type cells. In contrast, the transport of both thymidine and cytidine by JPA4 cells was similar to that of parental cells, and transport of these pyrimidine nucleosides remained sensitive to inhibition by both NBMPR and DPA. Furthermore, thymidine was a 10-12-fold weaker inhibitor of inosine transport in JPA4 cells than in wild type cells. Thus, JPA4 cells appeared to express two types of nucleoside transport activities; a novel (mutant) type that was insensitive to inhibition by DPA and NBMPR and transported purine nucleosides and uridine, and a parental type that retained sensitivity to inhibitors and transported cytidine and thymidine. The phenotype of the JPA4 cell line suggests that the sensitivity of mammalian nucleoside transporters to both NBMPR and DPA can be genetically uncoupled from its ability to transport certain nucleoside substrates and that the determinants on the nucleoside transporter that interact with each nucleoside are not necessarily identical.     

Supported phospholipid bilayers.

Phospholipid bilayers have been formed on glass, quartz, and silicon surfaces by a sequential transfer of two monolayers at a pressure of approximately 40 dyn/cm from the air-water interface to the solid substrates. Lateral diffusion measurements of L-alpha-dipalmitoylphosphatidylcholine (DPPC) bilayers supported on oxidized silicon wafers reveal two sharp phase transitions at temperatures similar to those found in multilayer systems with several different techniques. The diffusion measurements obtained using fluorescence recovery after pattern photobleaching provide evidence for the existence of an intermediate (probably P beta' or ripple) phase in single bilayers. While in the intermediate and high temperature (liquid-crystalline L alpha) phase, the diffusion coefficients do not vary very much with temperature, a strong temperature dependence is observed in the low temperature (gel L beta') phase. This is attributed to defect-mediated diffusion. Lipids in silicon supported bilayers made from L-alpha-dioleoylphosphatidylcholine (DOPC) or L-alpha-dimyristoylphosphatidylcholine (DMPC) diffuse rapidly above their respective chain-melting transition temperatures. Arrhenius plots show straight lines with activation energies of 40.9 and 43.7 kJ/mol, respectively. Supported DPPC bilayers on oxidized silicon form long tubular liposomes when heated through their oxidized silicon form long tubular liposomes when heated through their chain-melting-phase transition, as viewed with epifluorescence microscopy. It is suggested that this is a consequence of the expansion of the lipid on the fixed solid support. Conversely, DOPC bilayers form large void areas on this substrate upon cooling. Large circular membrane defects (holes) are observed under rapid coating conditions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Photochemical demonstration of stacked C.C+ base pairs in a novel DNA secondary structure

The secondary structure of the alternating polydeoxynucleotide sequence poly[d(C-T)] was studied as a function of pH by ultraviolet absorbance and circular dichroism spectroscopy and by the analysis of UV-induced photoproducts. As the pH was lowered, poly[d(C-T)] underwent a conformational transition that was characterized by changes in the long-wavelength region (280-320 nm) of the CD spectrum. These changes have previously been interpreted as evidence for the formation of a core of stacked, protonated C X C+ base pairs in a double-helical complex of poly[d(C-T)], with the thymidyl residues being looped out into the solvent [Gray, D. M., Vaughan, M., Ratliff, R. L., & Hayes, F. N. (1980) Nucleic Acids Res. 8, 3695-3707]. In the present work, poly[d(C-T)] was labeled with [U-14C]cytosine and [methyl-3H]thymine and irradiated at pH values both above and below the conformational transition point (monitored by CD spectroscopy). The distribution of radioactivity in uracil means value of uracil dimers, uracil means value of thymine dimers (the deamination products of cytosine means value of cytosine and cytosine means value of thymine dimers, respectively), and thymine-means value of thymine dimers was then determined. As the pH was decreased, we found an increase in the yield of uracil means value of uracil dimers and a decrease in the yield of uracil means value of thymine dimers, which occurred concomitantly with the change in the CD spectrum.(ABSTRACT TRUNCATED AT 250 WORDS)     

Studies on the Inoculation and Competitiveness of a Rhizobium leguminosarum Strain in Soils Containing Indigenous Rhizobia

The competitiveness of a Rhizobium leguminosarum strain was investigated at two separate locations in field inoculation studies on commercially grown peas. The soil at each location (sites I and II) contained an indigenous R. leguminosarum population of ca. 3 × 10⁴ rhizobia per g of soil. At site I it was necessary to use an inoculum concentration as large as 4 × 10⁷ CFU ml⁻¹ (2 × 10⁶ bacteria seed⁻¹) to establish the inoculum strain in the majority of nodules (73%). However, at site II the inoculum strain formed only 33% of nodules when applied at this (10⁷ CFU ml⁻¹) level. Establishment could not be further improved by increasing the inoculum concentration even as high as 10⁹ CFU ml⁻¹ (9.6 × 10⁷ bacteria seed⁻¹). The inoculum strain could be detected at both sites 19 months after inoculation. Analysis by intrinsic antibiotic resistance patterns and plasmid DNA profiles indicated that a dominant strain(s) and plasmid pool existed among the indigenous population at site II. Competition experiments were carried out under laboratory conditions between a dominant indigenous isolate and the inoculum strain. Both strains were shown to be equally competitive.     

Catalysis by heteropentalenes of electron transfer to oxygen from ferredoxin-NADP oxidoreductase reduced by NADPH

A range of heteropentalene and bipyridinium compounds have been tested as catalysts of electron transfer to oxygen from spinach ferredoxin-NADP⁺ oxidoreductase reduced by NADPH. For a particular class of compound, the rate of oxygen reduction increased with increasing midpoint potential of the compound under conditions in which reduction of the compound was rate-limiting. Compounds with similar midpoint potentials from different structural classes showed marked differences in rate, attributed to specificity in the interaction with ferredoxin-NADP⁺ oxidoreductase.     

A restriction endonuclease map of Streptomyces phage VWB

Summary A physical map of the actinophage VWB has been constructed using the restriction endonucleases BglII, ClaI, EcoRI, EcoRV, HindIII, KpnI and SphI. Phage VWB, genome size 47.3 kb, propagates on Streptomyces venezuelae, and it can also lysogenise this species. The three BglII-generated fragments of VWB DNA were cloned in pBR322, and subsequently mapped. In this manner the restriction map of the VWB phage genome was constructed.Abbreviations dam DNA adenine methylase activity - kb kilobase pairs - :: novel joint     

Distribution and recovery of15N after fertilization of Douglas-fir saplings with different nitrogen sources

Summary Four-year-old Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) saplings planted in pots with a sand and peat mix (11) were fertilized at the rate of 200 kg N/ha of (¹⁵NH₂)₂CO (U-15),¹⁵NH₄NO₃ (A-15) and NH₄ ¹⁵NO₃(An-15). They were placed in a shadehouse and watered regularly to maintain soil moisture at field capacity over periods of one and two years. Quantity of¹⁵N in foliage generally increased from old to current growth, irrespective of the nitrogen source. Utilization of¹⁵N fertilizers by saplings after the first and second growing seasons following fertilization was greatest with nitrate labelled ammonium nitrate AN-15, and nearly equal for urea U-15 and ammonium labelled ammonium nitrate A-15. The soil immobilized more fertilizer nitrogen-15 from U-15 and A-15 than from AN-15. Data from the present study, in which leaching losses of fertilizer were minimized, demonstrated that in terms of nitrogen uptake by the saplings the nitrate fertilizer was superior to ammonium fertilizer.     

Isolation and cryopreservation of O-methylthreonine-resistant Rosa cell lines altered in the feedback sensitivity of l-threonine deaminase

O-Methylthreonine (OMT) inhibits the growth of plated Rosa cells (ID₅₀6·10^-6M). Isoleucine is able to reverse efficiently and specifically this OMT toxicity. From OMT-resistant colonies occurring at a frequency of 1.58·10^-7 variants per cell plated at 10^-4M OMT, the variant strains OMT^R-1 and OMT^R-2 were isolated, cloned via protoplasts and characterized. Both variants were ten times more resistant to OMT than the wildtype and were cross-resistant to another isoleucine analog, dl-4-thiaisoleucine. The resistant variants retained their resistance after storage for three years in liquid nitrogen. Both resistant strains were stable for several months when subcultured in the absence of OMT although it was shown in a reconstitution experiment that wildtype cells overgrow OMT^R-2 variant cells if co-cultivated for many passages in drug-free medium. One case of instability was observed upon long-term subculturing in drug-free medium: the strain OMT^R-1D^* partially lost phenotypic properties. Resistance to OMT was followed qualitatively by a new method based on inhibition-zone formation in cell suspensions plated in agar medium. The OMT-resistant variants showed a reduction in sensitivity of the enzyme l-threonine deaminase to feedback inhibition by isoleucine, a decreased stability of l-threonine deaminase when stored at-18°C or incubated at +55°C and a two- to threefold increase of the free isoleucine pool within the cells. The genetical events and the biochemical mechanisms which might lead to the observed stable and biochemically defined character are discussed with particular reference to the high ploidy level of the Rosa cell line.Abbreviations OMT l-O-methylthreonine - TD l-threonine deaminase     

Cytochemical study of macrophage lysosomal inorganic trimetaphosphatase and acid phosphatase

Cytochemical investigations have associated acid inorganic trimetaphosphatase (TMPase) activity with the lysosomes of certain cell types. We have used the modified staining technique of Berg to show that this enzyme activity is present in normal mononuclear phagocytes and macrophage cell lines. We have found this enzyme activity to be present in murine RAW264 macrophages, in human U937 macrophages, in normal human blood monocytes, and in guinea pig peritoneal macrophages. All of the RAW264 and U937 macrophages showed intense TMPase activity. Many of the human monocytes and most of the guinea pig macrophages were labeled by this method. The reaction product was associated with the lysosomes of these cell types. The lysosomal staining-pattern was similar to that of acid phosphatase. Differences with regard to Golgi staining were noted. This indicates that TMPase is a lysosomal enzyme of mammalian macrophages. The distinction between TMPase and acid phosphatase activity has been demonstrated by measuring the pH optimum of each enzyme. Using substrates identical to those of the ultrastructural cytochemistry, we show that the pH optimum of TMPase is 4.0 and that of acid phosphatase is 5.0. The enzymatic activities are therefore ultrastructurally and biochemically distinct. Following phagocytosis of latex, yeast (Saccharomyces cerevisiae), or Corynebacterium parvum, TMPase has been found to be associated with phagosomes. This enzyme may take part in the degradation of phagocytosed materials, particularly microorganisms which contain inorganic polyphosphates and metaphosphates.