The Endoplasmic Reticulum and the Golgi Structures in Maize Root Cells

Maize root tips were fixed in potassium permanganate, embedded in epoxy resin, sectioned to show silver interference color, and studied with the electron microscope. All the cells were seen to contain an endoplasmic reticulum and apparently independent Golgi structures. The endoplasmic reticulum is demonstrated as a membrane-bounded, vesicular structure comparable in many aspects to that of several types of animal cells. With the treatment used here the membranes appear smooth surfaced. The endoplasmic reticulum is continuous with the nuclear envelope and, by contact at least, with structures passing through the cell wall. The nuclear envelope is characterized by discontinuities, as previously reported for animal cells. The reticula of adjacent cells seem to be in contact at or through the plasmodesmata. Because of these contacts the endoplasmic reticulum of a given cell appears to be part of an intercellular system. The Golgi structures appear as stacks of platelet-vesicles which apparently may, under certain conditions, produce small vesicles around their edges. Their form changes markedly with development of the cell.     

Aspartate and asparagine tRNA genes in wheat mitochondrial DNA: a cautionary note on the isolation of tRNA genes from plants.

We have identified genes encoding a "native" tRNA(Asp) (trnD-GTC) and a "chloroplast-like" tRNA(Asn) (trnN-GTT) on opposite strands and 633 bp apart within a sequenced 1640 bp RsaI restriction fragment of wheat mtDNA. The trnD gene has been found previously at a different location in wheat mtDNA (P.B.M. Joyce et al. (1988) Piant Mol. Biol. 11, 833-843); the duplicate copies of this gene are identical within the coding and immediate flanking regions (9 bp downstream and at least 68 bp upstream), after which obvious sequence similarity abruptly disappears. The trnN gene is identical to its homolog in maize ctDNA; continuation of sequence similarity beyond the coding region suggests that this gene originated as promiscuous ctDNA that is now part of the wheat mitochondrial genome. In the course of this work, we have encountered some unexpected similarities between tRNA gene regions from wheat mitochondria and other sources. Detailed analysis of these similarities leads us to suggest that trnN genes reportedly from petunia nuclear DNA (N. Bawnik et al. (1983) Nucleic Acids Res. 11, 1117-1122) and lupine mtDNA (B. Karpińska and H. Augustyniak (1988) Nucleic Acids Res. 16, 6239) are, in fact, from petunia mtDNA and lupine ctDNA, respectively, whereas a putative wheat nuclear tRNA(Ser) (trnS-TGA) gene (Z. Szwekowska-Kulińska et al. (1989) Gene 77, 163-167) is actually from wheat mtDNA. In these instances, it seems probable that the DNA samples used for cloning contained trace amounts of DNA from another sub-cellular compartment, leading to the inadvertent selection of spurious clones.     

Cerebrospinal fluid levels of immunoreactive substance P and somatostatin in patients with multiple sclerosis and inflammatory CNS disease.

Cerebrospinal fluid (CSF) levels of substance-P like immunoreactivity (SPLI) and somatostatin-like immunoreactivity (SLI) were measured in 43 patients with multiple sclerosis (MS), differentiated according to course and activity of the disease, in 23 patients with inflammatory disease of known bacterial or viral etiology and in 16 control patients using specific radioimmunoassay. SPLI and SLI levels were not significantly different from controls in MS patients whereas SLI was significantly increased in patients with infectious disease of central nervous system and/or subarachnoidal space. It is assumed that CSF SPLI and SLI cannot serve as a diagnostic or prognostic indicator of disease state in multiple sclerosis. Analysis of immunoreactivity by reverse phase HPLC-RIA revealed marked molecular heterogeneity of both neuropeptides.     

Elevated uridine nucleotide pools in fluorouracil/fluorouridine resistant mutants ofNocardia lactamdurans

Summary Selection of spontaneous mutants ofNocardia lactamdurans MA2908 for resistance to 5-fluorouracil results in the simultaneous development of resistance to 5-fluorouridine. The resulting mutants fall into four distinct classes based on the amount of uracil accumulating in fermentation broths. An additional characteristic of these mutants is a reduction in the ability to incorporate exogenous uracil into nucleic acids even though transport and conversion to the nucleotide level appears normal. Finally, production of efrotomycin is increased in these mutants in both chemically defined and complex fermentation media to levels equivalent to those of MA4820, the first productivity mutant isolated in a conventional strain improvement program. Resistance development and uracil excretion are adequately explained by an elevation of the intracellular uridine nucleotide pool, in particular UMP. The role of the uridine necleotides in the efrotomycin fermentation is unknown.     

Fetal cells in maternal blood: recovery by charge flow separation

Fetal blood cells can be recovered from the maternal circulation by charge flow separation (CFS), a method that obviates the risks associated with amniocentesis and chorionic villus sampling. By CFS, we processed blood samples from 13 women carrying male fetuses, 2 carrying fetuses with trisomy 21, and 1 who had delivered a stillborn infant with trisomy 18. On average more than 2000 fetal nucleated red blood cells were recovered per 20-ml sample of maternal blood. Recovery of fetal cells was confirmed by fluorescence in situ hybridization with probes for chromosomes Y, 18 and 21. After culturing of CFS-processed cells, amplification by the polymerase chain reaction revealed Y-chromosomal DNA in clones from four of six women bearing male fetuses, but not in clones from three women bearing female fetuses. Received: 8 January 1996 / Revised: 22 March 1996     

Presence of chromosomal mosaicism in abnormal preimplantation embryos detected by fluorescence in situ hybridisation

The extent of chromosomal mosaicism in human preimplantation embryos was examined using an improved procedure for the preparation and spreading of interphase nuclei for use in fluorescence in situ hybridisation, allowing the analysis of every nucleus within an embryo. One cell showed no hybridisation signals in only three of the 38 embryos that were included in this study, i.e. the hybridisation efficiency per successfully spread nucleus was 99% (197/200). Double-target in situ hybridisation analyses with X- and Y-chromosome-specific probes was performed to analyse nine embryos resulting from normal fertilisation, 22 polypronucleate embryos and seven cleavage-stage embryos where no (apronucleate) or only one pronucleus (monopronucleate) was observed. We also analysed autosomes 1 and 7 by double-target in situ hybridisation in the nuclei of two apronucleate, one monopronucleate and four polypronucleate embryos. All nine embryos that resulted from normal fertilisation were uniformly XY or XX. None of the apronucleate or monopronucleate embryos was haploid: three were diploid, one was triploid and three were mosaic. Fertilisation was detected by the presence of a Y-specific signal in four of these embryos. Of the polypronucleate embryos, two were diploid, two were triploid and 18 were mosaic for the sex chromosomes and/or autosomes 1 and 7. These results demonstrate that fertilisation sometimes occurs in monopronucleate embryos and that chromosomal mosaicism can be detected with high efficiency in apronucleate, monopronucleate and polypronucleate human embryos using fluorescence in situ hybridisation.     

A comparative study of glucose conversion to ethanol by Zymomonas mobilis and a recombinant Escherichia coli

Summary Zymomonas mobilis and recombinant Escherichia coli B (pLOI297) were compared in side-by-side batch fermentations using a synthetic cellulose hydrolysate (glucose/salts) medium with pH control at 6.0 and an inoculation cell density of 35–50 mg dry wt. cells/L. At a nominal glucose concentration of 6%, both cultures achieved near maximal theoretical ethanol yields; however, the Z. mobilis fermentation was complete at 13h compared to 33h for the E.coli fermentation. With approx.12% glucose, the Z. mobilis fermentation was complete in 20h with a process yield of 0.49 g ethanol/g added glucose compared to the E. coli fermentation which remained 20% incomplete after 6 days resulting in a process yield of only 0.32 g/g. Nutrient supplementation (10g tryptone/L) resulted in complete fermentation of 12% glucose (pH 6.3) by the recombinant E. coli in 4 days, with a yield of 0.48 g/g.