Light and electron microscopical postembedding lectin histochemistry for WGA-binding sites in the renal cortex of the mouse embedded in polyhydroxy aromatic resins LR-White and LR-Gold

Summary This work describes a technique which permits study of the postembedding lectin histochemistry for WGA-binding sites at the light and electron microscopical level on the same resin embedded tissue without removing or etching of the resin. Unfixed kidney pieces or kidney pieces fixed in 4% formaldehyde were embedded in the hydrophilic polyhydroxy aromatic resins LR-Gold and LR-White, following dehydration in up to 70% ethanol, 90% ethanol or 100% ethanol. LR-Gold was cryopolymerised at –25° C using the light sensitive initiator benzil, whereas LR-White was heat-cured at +50° C. The localisation of WGA-binding sites at the light microscopical level was investigated using FITC-labelled WGA. The ultrastructural localisation of WGA-binding sites was performed using 15 nm gold-labelled WGA. The best fluorescence staining results were obtained on fixed or unfixed tissue dehydrated in up to 70% ethanol and embedded in LR-Gold. At the ultrastructural level, the best staining results for WGA-binding sites were seen on tissue sections, dehydrated in up to 90% ethanol prior to embedding in LR-Gold.     

Appearance of lectin-binding sites during vascularization of the primordium of the central nervous system in 10 to 12-day-old mouse embryos

Summary In the present study lectin-binding sites were investigated for the lectins Ricinus communis agglutinin (RCA I), wheat germ agglutinin (WGA), soya bean agglutinin (SBA), concanavalin A (Con A), Lotus tetragonolobus(LTA) and Limulus polyphemus agglutinin (LPA) during the initial stages of vasculogenesis of the CNS-anlage in 10 to 12-day-old NMRI mouse embryos. Specific binding sites for the lectins RCA I (sugar specificity: -D-galactose, N-acetylgalactosamine), WGA (sugar specificity: N-acetylglucosamine, sialic acid), and SBA (sugar specificity: N-acetylgalactosamine, -D-galactose) were detected in the newly formed capillaries within the neuroepithelial cell layer. In contrast, binding sites for Con A, LTA and LPA could not be observed at the start of the vascularization of the CNS-anlage. From these results, the conclusion can be drawn that glycoconjugates containing D-galactose, N-acetylgalactosamine and N-acetyl-glucosamine moieties are involved in the early vasculogenesis of the embryonic CNS-anlage of the mouse.     

Transgenic mice generated by pronuclear injection of a yeast artificial chromosome.

Transgenic mice have become invaluable for analysing gene function and regulation in vivo. However, the size of constructs injected has been limited by the cloning capacity of conventional vectors, a constraint that could be overcome with yeast artificial chromosomes (YACs). We investigated the feasibility of making transgenic mice with YACs by pronuclear injection of a small YAC carrying a gene encoding tyrosinase. Use of a vector with a conditional centromere allowed fifteenfold amplification of the YAC in yeast and its recovery in high yield. The albino phenotype of the recipient mice was rescued demonstrating the correct expression of the tyrosine gene from the construct. Furthermore, the telomeric sequences added by the yeast integrated into the mouse genome and did not reduce efficiency of integration. Using this technique future experiments with longer YACs will allow the expression of gene complexes such as Hox and the globin gene clusters to be analysed in transgenic animals.     

Physical mapping of two Xp markers DXS16 and DXS143

Summary Lymphocyte karyotyping of an infant girl with the clinical features of microphthalmia, iridoschisis, goiter, hip joint dysplasia, labium synechia and craniotabes revealed an Xp deletion. The lymphocyte karyotypes of the parents were normal. Bromodeoxyuridine incorporation studies showed that, in 42 out of 43 metaphases, the deleted X chromosome was late replicating. In one metaphase, the normal X chromosome was observed to be allocyclic. Using DNA markers from the Xp22 region, the breakpoint was assigned distal to DXS16 (pXUT23) and proximal to DXS143 (dic56). Dosage intensity measurements confirmed that the STS gene and the DNA marker DXS31 were involved in the deleted area. Restriction fragment length polymorphism analysis revealed that the paternally derived X-chromosome was deleted.     

Xenobiotic biotransformation in unicellular green algae. Involvement of cytochrome P450 in the activation and selectivity of the pyridazinone pro-herbicide metflurazon.

The N-demethylation of the pyridazinone pro-herbicide metflurazon into norflurazon implies a toxification in photosynthetic organisms. This is confirmed by quantitative structure activity relationships determined for two unicellular green algae, Chlorella sorokiniana and Chlorella fusca; however, the latter is 25 to 80 times more sensitive to metflurazon. This sensitivity is linked to differences in the N-demethylase activity of both algae, as determined by an optimized in vivo biotransformation assay. Apparent K(m) values of the metflurazon-N-demethylase indicate a 10-fold higher affinity for this xenobiotic substrate for Chlorella fusca. Furthermore, algal metflurazon-N-demethylation is characterized by distinct variations in activity, depending on the stage of cell development within the cell cycle. Several well-established inhibitors of cytochrome P450-mediated reactions, including piperonylbutoxide, 1-aminobenzotriazole, 1-phenoxy-3-(1H-1,2,4-triol-1yl)-4-hydroxy-5,5-dimethylhexane++ +, and tetcyclacis, as well as cinnamic acid, a potential endogenous substrate, inhibited the N-demethylation of metflurazon. The results suggest that the N-demethylation of metflurazon by both algae is mediated by a cytochrome P450 monooxygenase. The determination of antigenic cross-reactivity of algal proteins with heterologous polyclonal antibodies originally raised against plant P450s, anti-cinnamic acid 4-hydroxylase (CYP73A1), anti-ethoxycoumarin-O-dealkylase, anti-tulip allene oxidase (CYP74), and an avocado P450 (CYP71A1) or those of bacterial origin, CYP105A1 and CYP105B1, suggests the presence of distinct P450 isoforms in both algae.     

Effects of the detergent Tween 80 on Thermomonospora curvata

Tween 80 (0.1%, v/v) added to Thermomonospora curvata growing in minimal medium caused a transient lowering of the dry cell mass, decreased the optimal growth temperature of the thermophile from 62 to 54°C, and increased extracellular esterase activity. Cells grown in the presence of Tween 80 had decreased concentrations of branched chain fatty acids and increased concentrations of oleic acid. The detergent removed surface protuberances from mycelia and increased the liberation of enzymes active against crystalline cellulose, but did not stimulate liberation of enzymes active against carboxymethylcellulose, starch or pectin.     

An Ustilago maydis Mutant Partially Blocked in P45014DM Activity Is Hypersensitive to Azole Fungicides

An Ustilago maydis ergosterol biosynthesis mutant (A14) which is partially blocked in sterol 14alpha-demethylase (P45014DM) activity is described. This mutant accumulated the abnormal 14alpha-methyl sterols, eburicol, 14alpha-methylfecosterol, and obtusifoliol, along with significant amounts of ergosterol. Although the A14 mutant grew nearly as well as the wild type, it was impaired in cell extension growth, which indicated a dysfunction in apical cell wall synthesis. The mutant was also found to be hypersensitive to the azole fungicides penconazole and tebuconazole.     

Carbon isotope composition of N2-fixing and N-fertilized legumes along an elevational gradient

Dinitrogen-fixing legumes are frequently assumed to be less water-use efficient than plants utilizing soil mineral N, because of the high respiratory requirements for driving N₂ fixation. However, since respiration is assumed not to discriminate against ¹³C, any differences in water-use efficiency exclusively due to respiration should not be apparent in carbon isotope discrimination () values. Our objective was to determine if the source of N (N₂ fixation versus soil N) had any effect on of field-grown grain legumes grown at different elevations. Four legume species, Glycine max, Phaseolus lunatus, P. vulgaris, and Vigna unguiculata, were grown on five field sites spanning a 633 m elevational gradient on the island of Maui, Hawaii. The legumes were either inoculated with a mixture of three effective strains of rhizobia or fertilized weekly with urea at 100 kg N ha^-1 in an attempt to completely suppress symbiotic N₂-fixing activity. In 14 of 20 analyses of stover and 12 of 15 analyses of seed values were significantly higher (p=0.10) in the inoculated plants than the N-fertilized plants. Nitrogen concentrations were generally higher in the fertilized treatments than the inoculated treatments. The different values obtained depending on N-source may have implications in using as an indicator of water-use efficiency or yield potential of legumes.     

X-ray solution scattering reveals conformational changes upon iron uptake in lactoferrin, serum and ovo-transferrins.

X-ray solution scattering has been used for studying the structural changes that take place upon uptake and release of iron from serum and chicken ovo-transferrin and human lactoferrin. In the case of chicken ovo-transferrin, data have been obtained for both the intact protein and the isolated N and C-lobes with and without iron. These studies reveal that both lobes undergo a change that is consistent with an opening of the inter-domain cleft when iron is removed from the protein. We suggest that the conformational change of the protein increases the specificity of receptor binding and that the closed configuration of the iron-loaded protein is one, or perhaps the, decisive step in the mechanism for receptor-mediated endocytosis.