Two-dimensional electrophoresis patterns of total proteins,esterases and acid phosphatases from pollen,seeds and leaves of three cultivars of Helianthus annuus L

Total proteins, esterases and acid phosphatases from pollen, seeds and leaves of three sunflower cultivars were separated by 2-D electrophoresis. The characteristic peptides for each cultivar were identified. The seeds and pollen of the cultivar Wielkopolski contained 45 and 37 characteristic peptides, respectively, while the seeds and pollen of Coril contained 73 and 35 characteristic peptides. The cultivar Frankasol had the lowest total number of stained peptides in seeds and pollen, and the number of the characteristic peptides was only 61 and 25, respectively. Analyses of esterases and acid phosphatases from young leaves and pollen led to identification of isoenzymes characteristic of the three cultivars. Only for Frankasol no specific acid phosphatase was observed, both in leaves and in pollen.     

Site of the previous meiotic division defines cleavage orientation in the mouse embryo

The conservation of early cleavage patterns in organisms as diverse as echinoderms and mammals suggests that even in highly regulative embryos such as the mouse, division patterns might be important for development. Indeed, the first cleavage divides the fertilized mouse egg into two cells: one cell that contributes predominantly to the embryonic part of the blastocyst, and one that contributes to the abembryonic part. Here we show, by removing, transplanting or duplicating the animal or vegetal poles of the mouse egg, that a spatial cue at the animal pole orients the plane of this initial division. Embryos with duplicated animal, but not vegetal, poles show abnormalities in chromosome segregation that compromise their development. Our results show that localized factors in the mammalian egg orient the spindle and so define the initial cleavage plane. In increased dosage, however, these factors are detrimental to the correct execution of division.     

Difficulties in the deprotection of 1,2-ketals in nucleosides containing alkylidencarbazoyl groups

The synthesis of unprotected alkylidencarbazoyl nucleoside derivatives 8a-8d is shown. A direct deprotection route from readily available 2',3'-isopropylidene protected nucleosides 5a-5d. prepared from a chemoenzymatic procedure, did not give the selective cleavage of the ketal function without affecting the C=N bond. The next option tried was to look at the previous compound in the retrosynthetic route: 2',3'-protected carbazoyl nucleoside 4. However, in all cases we obtained unsatisfactory results. Stepping further back, the hydrolysis of compound 3a led us to unprotected carbonate nucleoside 9 in quantitative yield. With this compound available, the synthesis towards derivatives 8 was accomplished through a known procedure.     

Efficient delivery of dsRNA into zona-enclosed mouse oocytes and preimplantation embryos by electroporation

Conditions for the electroporation of mouse oocytes and preimplantation embryos have been optimised by following the incorporation of rhodamine labeled dextran. This procedure includes a step to weaken but not remove the zona pellucida that helps achieve good survival. This approach has been applied to introduce double-stranded RNA for c-mos into oocytes and green fluorescent protein (GFP) into transgenic GFP-expressing embryos at the 1- and 4-cell stages. In both cases we were able to observe sequence-specific interference with the expression of the target gene--a failure of oocytes to arrest at metaphase II and a loss in the green fluorescence of embryos by the morula or blastocyst stages. These effects could be observed in multiple oocytes or embryos allowed to develop together following electroporation.     

Supramolecular ligands: Monomer structure and protein ligation capability

The aim of this work was to define the chemical structure of compounds self-assembling in water solutions, which appear to interact with proteins as single ligands with their supramolecular nature preserved. For this purpose the ligation to proteins of his azo dyes, represented by Congo red and its derivatives with designed structural alterations, were tested. The three parameters which characterize the reactivity of supramolecular material were determined in the same conditions for all studied dyes. These were: A) stability of the assembly products; B) binding to heat-denatured protein (human IgG); and C) binding to native protein (rabbit antibodies in the immune complex) measured by the enhancement of hemagglutination. The structural differences between the Congo red derivatives concerned the symmetry of the molecule and the structure of its non-polar component, which occupies the central part of the dye molecule and is thought to be crucial for self-assembly. Other dyes were also studied for the same purpose: Evans blue and Trypan blue, bis-ANS and ANS, as well as a group of compounds with a structural design unlike that of bis azo dyes. Compounds with rigid elongated symmetric molecules with a large non-polar middle fragment are expected to form a ribbon-like supramolecular organization in assembling. They appeared to have ligation properties related to their self-assembling tendency. The compounds with different structures, not corresponding to his azo dyes, did not reveal ligation capability, at least in respect to native protein. The conditions of binding to denatured proteins seem less restrictive than the conditions of binding to native molecules. The molten hydrophobic protein interior becomes a new binding area allowing for complexation of even non-assembled molecules.     

Different UmuC requirements for generation of different kinds of UV-induced mutations in Escherichia coli

An Escherichia coli strain bearing the dnaQ49 mutation, which results in a defective s subunit of DNA polymerase III, and carrying the lexA71 mutation, which causes derepression of the SOS regulon, is totally unable to maintain high-copy-number plasmids containing the umuDC operon. The strain is also unable to maintain the pAN4 plasmid containing a partial deletion of the umuD gene but retaining the wild-type umuC gene. These results suggest that a high cellular level of UmuC is exceptionally harmful to the defective DNA polymerase III of the dnaQ49 mutant. We have used this finding as a basis for selection of new plasmid umuC mutants. The properties of two such mutants, bearing the umuC61 or umuC95 mutation, are described in detail. In the umuC122:: Tn 5 strain harbouring the mutant plasmids, UV-induced mutagenesis is severely decreased compared to that observed with the parental umuDC ⁺ plasmid. Interestingly, while the frequency of UV-induced GC AT transitions is greatly reduced, the frequency of AT TA transversions is not affected. Both mutant plasmids bear frameshift mutations within the same run of seven A residues present in umuC ⁺; in umuC61 the run is shortened to six A whereas in umuC95 is lengthened to eight A. We have found in both umuC61 and umuC95 that translation is partially restored to the proper reading frame. We propose that under conditions of limiting amounts of UmuC, the protein preferentially facilitates processing of only some kinds of UV-induced lesions.     

Cytoskeletal organization of rat oocytes during metaphase II arrest and following abortive activation: A study by confocal laser scanning microscopy

In metaphase II arrested rat oocytes (M il), microtubles were found in the taper-shaped meiotic spindle and in the cytoplasm as asters and free microtubules. Whereas spindle microtubules were acetylated, those located in the cytoplasm were not. Cytoplasmic microtubules were also labile as assessed by mild cooling. In contast to mouse oocytes, rat microtubule organizing centers (MTOCs) did not react with MPM-2 antibody by immunofluorescence despite the fact that this antibody reacts with several proteins as shown by immunoblot. However, cytoplasmic MTOCs in M II-arrested rat oocytes could be detected by their nucleating capacity in the presence of taxol, a drug that induced the formation of numerous cytoplasmic asters. In addition, taxol caused a change in the spindle shape and the formation of astral microtubules at the spindle poles. Meiotic spindles (as well as chromosomes devoid of microtubules after nocodazoletreatment) were overlaid by an actin-rich domain. Spontaneous abortive activation led to the extrusion of the second polar body followed by another metaphase arrest— metaphase III; however, normal spindles did not form and dispersed chromosomes surrounded by microtubles were observed. Electron microscopic studies confirmed these observations and revealed that the kinetochores are located deep within the chromosomes in contrast to mouse kinetochores, and this might be responsible for the absence of a metaphase III spindle in the rat oocyte. Induced activation caused transition to interphase with the formation of a characteristic microtubule network. This study shows that there are several significant differences in the cytoskeletal organization of rat and mouse oocytes. © 1993 Wiley-Liss, Inc.     

Sensory irritation and taste produced by NaCl and citric acid: effects of capsaicin desensitization

Three experiments were conducted to measure the sensory irritationproduced by two prototypical gustatory stimuli: citric acidand NaCl. The stimuli were applied to the tip of the tongueon filter paper disks. The first experiment revealed that solutionsof NaCl and citric acid that produced approximately equal tastesensations also produced similar amounts of irritation; thatthe psychophysical functions for irritation were approximatelytwice as steep as the functions for taste; and that irritationgrew over time for NaCl but not for citric acid. When viewedas a percentage of the taste sensation at 25 s, NaCl irritationaveraged 23% at the lowest concentration and 70% at the highestconcentration; citric acid irritation averaged 44% at the lowestconcentration and 98% at the highest concentration. The secondexperiment investigated whether the irritation produced by thesetwo stimuli was mediated via capsaicin-sensitive (CS) fibers.The experiment included a pre-test, an irritation treatmentwith either capsaicin (a desensitizing agent) or zingerone (anon-desensitizing agent), a 15 min rest period and a post-test.Reductions in irritation and taste occurred following treatmentwith both capsaicin and zingerone. A third experiment demonstratedthat the majority of the effect of zingerone on taste and irritationwas due to a perceptual context effect. After the context effectwas taken into account, capsaicin desensitization remained significantfor both salt taste and salt irritation at the highest concentration.A similar pattern of results for citric acid suggests that bothcitric acid and NaCl produce irritation in part via CS fibers.The results are discussed in terms of the ability of subjectsto discriminate the gustatory and chemesthetic components oforal sensations and the role of salt and acid irritation inflavor perception.     

Phenylketonuria in Spain: RFLP haplotypes and linked mutations

In order to investigate the molecular basis of phenylketonuria (PKU) in Spain, we analyzed the restriction fragment length polymorphism (RFLP) haplotypes and common mutations in the phenylalanine hydroxylase (PAH) gene in 32 unrelated Spanish PKU families. The distribution of RFLP haplotypes differs from that of northern Europe. Mutant haplotypes 2 and 3 were completely absent in our sample. Approximately 65% of the mutant alleles are confined to three RFLP haplotypes, namely haplotypes 1, 6 and 9, also frequently found in other Mediterranean populations. We screened for previously described PKU mutations using the polymerase chain reaction and allele-specific oligonucleotides, and found IVS10,165T, E280K and P281L as the major mutations, representing 41% of the PKU alleles. Other mutations found were Y414C, and a new one, P244L. Mutations R408W and IVS12, prevalent in northern Europe, as well as others present in southern European populations (R252W, R261Q, L249F) were not detected in our sample. Our results reveal the genetic heterogeneity present in the Spanish PKU population, which shows similarities to others of Mediterranean origin.