Importance of seed Zn content for wheat growth on Zn-deficient soil

Eggplants (Solanum melongena L. cv. Bonica) were grown in a glasshouse during summer under natural light with one unbranched shoot or one shoot with 3 to 4 branches and with or without fruit in quartz sand buffered and not buffered with 0.5% CaCO₃ (w : v), respectively. Nutrient solutions supplied contained nitrate or ammonium as the sole nitrogen source. Compared with nutrient solutions containing nitrate (10 mM), solutions containing ammonium (10 mM) caused a decrease in net photosynthesis of eggplants during early stages of vegetative growth when grown in quartz sand not buffered with CaCO₃. The decrease was not observed before leaves showed interveinal chlorosis. In contrast, net photosynthesis after bloom at first increased more rapidly in eggplants supplied with ammonium than with nitrate nitrogen. However, even in this case, net photosynthesis decreased four weeks later when ammonium nutrition was continued. The decrease was accompanied by epinasty and interveinal chlorosis on the lower leaves and later by severe wilting, leaf drop, stem lesions, and hampered growth of stems, roots, and fruits. These symptoms appeared later on plants not bearing fruits than on plants bearing fruits. If nutrient solutions containing increasing concentrations of ammonium (0.5–30 mM) were supplied after the time of first fruit ripening, shoot growth and set of later flowers and fruits were promoted. In contrast, vegetative growth and reproduction was only slightly affected by increasing the concentration of nitrate in the nutrient solutions. In quartz sand buffered with CaCO₃ ammonium nutrition caused deleterious effects only under low light conditions (shade) and on young plants during rapid fruit growth. If eggplants were supplied with ammonium nitrogen before bloom, vegetative growth was promoted, and set of flowers and fruit occurred earlier than on plants supplied with nitrate. Furthermore, the number of flowers and fruit yield increased. These effects of ammonium nutrition were more pronounced when plants were grown with branched shoots than with unbranched shoots. The results indicate that vegetative and reproductive growth of eggplants may be manipulated without causing injury to the plants by supplying ammonium nitrogen as long as the age of the plants, carbohydrate reserves of the roots, quantity of ammonium nitrogen supplied, and pH of the growth medium are favourable. T W Rufty Section editor     

Electrotransfection of Propionibacterium freudenreichii TL 110

The first highly efficient protocol is described for the electrotransfection of Propionibacterium freudenreichii with DNA phage. The transfection efficiency is 7 times 10⁵ transfectants per μg of DNA under optimal conditions. Optimized parameters included the field strength (12.5 kV, 200 Ohms, 25 μF), phage DNA concentration (1 μg ml^-1) and cell density (1.5 times 10¹⁰ cells ml^-1). Growth in the presence of glycine and harvesting of cells during the early exponential growth phase increased the transfection efficiency. This electrotransfection protocol is of importance for the genetic improvement of dairy propionibacteria.     

Mixed anion lanthanide(III) crown ether complexes: crystal structures of [LaCl2(NO3)(12-crown-4)]2, [La(NO3)(OH2)4-(12-crown-4)]Cl2·CH3CN and [LaCl2(NO3)(18-crown-6)]

Reaction of LaCl₃·7H₂O containing small amounts of La(NO₃)₃·7H₂O as an impurity with 12-crown-4 or 18-crown-6 in 3:1 CH₃CN:CH₃OH resulted in the isolation of the mixed anion complexes [LaCl₂(NO₃)(12-crown-4)]₂, [La(NO₃)(OH₂)₄(12-crown-4)]Cl₂·CH₃CN and [LaCl₂(NO₃)(18-crown-6)]. The nine-coordinate dimer, [LaCl₂(NO₃)(12-crown-4)]₂, has all of the anions in the inner coordination sphere and La³⁺ has a capped square antiprismatic geometry. It crystallizes in the orthorhombic space group Pbca with (at −150 °C) a = 12.938(6), B = 15.704(3), C = 13.962(2) Å, and D_calc = 2.08 g cm⁻³ for Z = 4. The second complex isolated from the same reaction, [La(NO₃)(OH₂)₄(12-crown-4)]Cl₂·CH₃CN, has the bidentate nitrate anion in the inner coordination sphere but the two chloride anions are in a hydrogen bonded outer sphere. This complex is ten-coordinate 4A,6B-expanded dodecahedral and crystallizes in the monoclinic space group P2₁ with (at 20 °C) A = 7.651(2), B = 11.704(7), C = 11.608(4) Å, β = 95.11(2)°, and D_calc = 1.80 g cm⁻³ for Z = 2. The 18-crown-6 complex, [LaCl₂(NO₃)(18-crown-6)], has all inner sphere anions and has ten-coordinate 4A,6B-expanded dodecahedral La³⁺ centers. It crystallizes in the orthorhombic space group Pbca with (at 20 °C) a = 14.122(7), B = 13.563(5), C = 19.311(9) Å, and D_calc = 1.89 g cm⁻³ for Z = 8.     

Regulatory action of prolactin on the in vitro growth of CD34+ve human hemopoietic progenitor cells

The pituitary hormone prolactin (Prl) is known to act as a local regulator of immune cell function, and Prl-binding receptors (Prl-R) have been described to share distinctive features with the members of the newly described cytokine/hemopoietin receptor superfamily. Here we show that the hormone can functionally interact with lineage-specific hemopoietic factors. When highly purified progenitor cells (CD34+ve) were seeded in semisolid methylcellulose cultures in the presence of interleukin (IL)-3, granulocyte-macrophage colony stimulating factor (GM-CSF), and erythropoietin (Epo), a selective enhancing effect of Prl on the formation of colony forming unit-granulocyte (CFU-G) and burst forming unit-erythroid (BFU-E) colonies was observed. The effect of the hormone was plotted as a bell shaped curve, with the optimal response at the supraphysiological concentration of 50 ng/ml. Limiting dilution analysis showed that Prl acted directly on hemopoietic progenitors. This was confirmed by the observation on the CD34+ve cells of Prl-binding sites reacting with the specific monoclonal antibodies (mAbs), U5 and PrR-7A. Immunoprecipitation of the metabolically labeled CD34+ve cells with the PrR-7A mAb revealed a structure of 43 kD under reducing conditions. Analysis of the early events associated with the Prl/Prl-R interaction showed an increased number of cells engaged in DNA and hemoglobin synthesis. Enhanced erythroid differentiation of CD34+ve cells in the presence of Prl was secondary to upmodulation of receptors for the lineage-specific factor Epo. Together these data demonstrate the existence of a functional interplay between Prl. and hemopoietic factors. © 1995 Wiley-Liss, Inc.     

Statistical analysis of vertebrate sequences reveals that long genes are scarce in GC-rich isochores

We compared the exon/intron organization of vertebrate genes belonging to different isochore classes, as predicted by their GC content at third codon position. Two main features have emerged from the analysis of sequences published in GenBank: (1) genes coding for long proteins (i.e., 500 aa) are almost two times more frequent in GC-poor than in GC-rich isochores; (2) intervening sequences (=sum of introns) are on average three times longer in GC-poor than in GC-rich isochores. These patterns are observed among human, mouse, rat, cow, and even chicken genes and are therefore likely to be common to all warm-blooded vertebrates. Analysis of Xenopus sequences suggests that the same patterns exist in cold-blooded vertebrates. It could be argued that such results do not reflect the reality because sequence databases are not representative of entire genomes. However, analysis of biases in GenBank revealed that the observed discrepancies between GC-rich and GC-poor isochores are not artifactual, and are probably largely underestimated. We investigated the distribution of microsatellites and interspersed repeats in introns of human and mouse genes from different isochores. This analysis confirmed previous studies showing that Ll repeats are almost absent from GC-rich isochores. Microsatellites and SINES (Alu, B1, B2) are found at roughly equal frequencies in introns from all isochore classes. Globally, the presence of repeated sequences does not account for the increased intron length in GC-poor isochores. The relationships between gene structure and global genome organization and evolution are discussed.     

Regulation of Osteoblast Gene Expression in Intratypic Osteosarcoma Hybrid Cells

Intratypic osteosarcoma hybrids were constructed by fusing the human osteoblast-like osteosarcoma SaOS-2 with the rat osteoblast-like osteosarcoma UMR-106. Both of these osteosarcomas express liver/bone/kidney alkaline phosphatase (ALPL), but only the UMR-106 cell line expresses osteopontin (OPN), a gene expressed during later stages of osteoblast differentiation. Analysis of osteoblast gene expression in these hybrids demonstrated that ALPL continued to be expressed; however, OPN steady-state mRNA levels were dramatically reduced in four hybrids. Quantitative measurements indicated theft OPN steady-state mRNA levels were extinguished by a factor of 20- to 1000-fold. Since SaOS-2 chromosomes are preferentially lost from these hybrids, subclones of extinguished hybrids were isolated that reexpressed OPN mRNA at levels similar to the UMR-106 parental line. These data indicate that trans-acting negative regulatory factors, expressed from the SaOS-2 genome, are responsible for OPN extinction. This report provides the first demonstration of the negative regulation of OPN gene expression and also provides additional evidence that extinction plays a role in the regulation of osteoblast gene expression.     

Solution properties ofEscherichia coli-expressed VH domain of anti-neuraminidase antibody NC41

The V_H domain of anti-influenza neuraminidase antibody NC41, with and without a C-terminal hydrophilic marker peptide (FLAG^TM), has been expressed in high yield (15–27 mg/L) inEscherichia coli. Both forms were secreted into the periplasm where they formed insoluble aggregates which were solubilized quantitatively with 2 M guanidine hydrochloride and purified to homogeneity by ion-exchange chromatography. The V_H-FLAG was composed of three isoforms (pI values of 4.6, 4.9, and 5.3) and the V_H molecule was composed of two isoforms with pI values of 5.1 and 6.7; the difference between the V_H isoforms was shown to be due to cyclization of the N-terminal glutamine residue in the pI 5.1 isoform. At 20°C and concentrations of 5–10mg/ml the V_H domain dimerized in solution and then partly precipitated, resulting in the broadening of resonances in its¹H NMR spectrum. Reagents such as CHAPS,n-octylglucoside, and ethylene glycol, which presumably mask the exposed hydrophobic interface of the V_H molecule, prevented dimerization of the V_H and permitted good-quality NMR spectra on isotope-labeled protein to be obtained.     

Male-specific cell migration into the developing gonad

Background: The gene Sry acts as a developmental switch, initiating a pathway of gene activity that leads to the differentiation of testis rather than ovary from the indifferent gonad (genital ridge) in mammalian embryos. The early events following Sry expression include rapid changes in the topographical organization of cells in the XY gonad. To investigate the contribution of mesonephric cells to this process, gonads from wild-type mice (CD1), and mesonephroi from a transgenic strain ubiquitously expressing β-galactosidase (ROSA26), were grafted together in vitro. After culture, organs were fixed and stained for β-galactosidase activity to identify cells contributed from the mesonephros to the male or female gonad.Results: Migration of mesonephric cells occurred into XY but not XX gonads from 11.5–16.5 days post coitum (dpc). Somatic cells contributed from the mesonephros were distinguished by their histological location and by available cell-specific markers. Some of the migrating cells were endothelial; a second population occupied positions circumscribing areas of condensing Sertoli cells; and a third population lay in close apposition to endothelial cells.Conclusions: Migration from the mesonephros to the gonad is male specific at this stage of development and depends on an active signal that requires the presence of a Y chromosome in the gonad. The signals that trigger migration operate over considerable distances and behave as chemoattractants. We suggest that migration of cells into the bipotential gonad may have a critical role in initiating the divergence of development towards the testis pathway.