The zygote and proembryo of alfalfa: quantitative,three-dimensional analysis and implications for biparental plastid inheritance

Summary Genetic studies have demonstrated biparental inheritance of plastids in alfalfa. The ratio of paternal to maternal plastids in the progeny varies according to the genotypes of the parents, which can be classified as strong or weak transmitters of plastids. Previous cytological investigations of generative cells and male gametes have provided no consistent explanation for plastid inheritance patterns among genotypes. However, plastids in the mature egg cells of a strong female genotype (6–4) were found to be more numerous and larger than in mature eggs of a weak female genotype (CUF-B), and the plastids in 6–4 eggs are positioned equally around the nucleus. In CUF-B, the majority of plastids are positioned below (toward the micropyle) the mid level of the nucleus, which is the future division plane of the zygote. Since only the apical portion of the zygote produces the embryo proper, plastids in the basal portion were predicted to become included in the suspensor cells and not be inherited. In the present study, we examined zygotes and a two-celled proembryo from a cross between CUF-B and a strong male genotype (301), a cross that results in over 90% of the progeny possessing paternal plastids only. Our results indicate that the distribution of plastids observed in the CUF-B egg cell is maintained through the first division of the zygote. Further, paternal plastids are similarly distributed; however, within the apical portion of the zygote and in the apical cell of the two-celled proembryo, the number of paternal plastids is typically much greater than the number of maternal plastids. These findings suggest that maternal and paternal plastid distribution within the zygote is a significant factor determining the inheritance of maternal and paternal plastids in alfalfa.     

Enhanced expression of cellular receptors for human interferon α on peripheral lymphocytes from patients with down''s syndrome

The sequence of 370 bases at the 5′-end of bovine thyroglobulin mRNA has been determine. A41 base untranslated segment was found preceeding the ATG initiator codon. It is followed by an open reading frame providing the first data on thyroglobulin primary structure. Analysis of the amino acid sequence demonstrated the presence of an 18 residue hydrophobic segment representing a putative signal peptide. Comparison of the amino terminal sequence of thyroglobulin with that of peptides known to contain thyroid hormones [7,8] demonstrated that the first tyrosine in native thyroglobulin is mainly found as thyroxine in the mature iodinated protein [8]. Our results clearly identify the amino-terminal region of thyroglobulin as an important hormonogenic domain of the protein.     

Two closely linked tomato HKT coding genes are positional candidates for the major tomato QTL involved in Na+/K+ homeostasis

The location of major quantitative trait loci (QTL) contributing to stem and leaf [Na⁺] and [K⁺] was previously reported in chromosome 7 using two connected populations of recombinant inbred lines (RILs) of tomato. HKT1;1 and HKT1;2, two tomato Na⁺‐selective class I‐HKT transporters, were found to be closely linked, where the maximum logarithm of odds (LOD) score for these QTLs located. When a chromosome 7 linkage map based on 278 single‐nucleotide polymorphisms (SNPs) was used, the maximum LOD score position was only 35 kb from HKT1;1 and HKT1;2. Their expression patterns and phenotypic effects were further investigated in two near‐isogenic lines (NILs): 157‐14 (double homozygote for the cheesmaniae alleles) and 157‐17 (double homozygote for the lycopersicum alleles). The expression pattern for the HKT1;1 and HKT1;2 alleles was complex, possibly because of differences in their promoter sequences. High salinity had very little effect on root dry and fresh weight and consequently on the plant dry weight of NIL 157‐14 in comparison with 157‐17. A significant difference between NILs was also found for [K⁺] and the [Na⁺]/[K⁺] ratio in leaf and stem but not for [Na⁺] arising a disagreement with the corresponding RIL population. Their association with leaf [Na⁺] and salt tolerance in tomato is also discussed.     

Hydrophobic cluster analysis reveals duplication in the external structure of human alpha-interferon receptor and homology with gamma-interferon receptor external domain

Evidence is presented, based on sequence comparison according to Hydrophobic Cluster Analysis, of a structural and evolutionary relationship between the human alpha/beta-interferon receptor and the human and mouse gamma-interferon receptor. These results predict that the human alpha/beta-interferon receptor extracellular part is organised in two homologous subdomains connected by a proline linker. They also predict that both subdomains present some homologies to the external domain of mouse and human gamma interferon receptor.     

Diagnostic criteria for diabetes revisited: making use of combined criteria

Background  

Existing cut-offs for fasting plasma glucose (FPG) and post-load glucose (2hPG) criteria are not equivalent in the diagnosis of diabetes and glucose intolerance. Adjusting cut-offs of single measurements have not helped so we undertook this project to see if they could be complementary.     

Quantitative cytology of the alfalfa generative cell and its relation to male plastid inheritance patterns in three genotypes

Summary Studies utilizing restriction analysis of plastid DNA, as well as those employing chlorophyll-deficient mutants, have shown a high frequency of paternal plastid transmission in alfalfa. Recent research has also shown that plastid inheritance patterns among alfalfa genotypes and are under genetic control. In a previous study we were unable to detect any correlations between qualitative, three-dimensional ultrastructure of generative cells and male plastid transmission strength in certain genotypes. In the present study we used serial ultrathin sectioning, computerized reconstruction and quantitation, and stereology to further analyze generative cells within mature pollen. Measurements included volumes and surface areas of cells, nuclei, and organelles, as well as organelle number and distribution. Three genotypes were investigated, one that is a strong transmitter of male plastids (genotype 301), one that is a weaker transmitter of male plastids (genotype 7W), and a third that is an even weaker male plastid transmitter (genotype MS-5). Our results show that genotype MS-5 has significantly fewer plastids/generative cell than either of the other genotypes, which may account for it being a relatively poor transmitter of male plastids. However, plastid number does not explain known differences in male plastid inheritance between genotypes 301 and 7W, since plastid number does not differ significantly between these two genotypes. Regarding the other features of generative cells measured in this study, no consistent correlations were found that might account for differences in male plastid inheritance patterns between genotypes. Plastid distribution is equal in each end of the spindle-shaped generative cell in all genotypes studied. Similar relative results were found with regard to mitochondria within generative cells; however, comparative genetic data are not available on mitochondrial transmission patterns in alfalfa genotypes.     

On the identity of Festuca jubata Lowe (Poaceae) and the description of a new Festuca species in the Azores Islands

The majority of authors consider Festuca jubata Lowe as an endemic species common to Madeira and the Azores. Saint-Yves proposed that F. jubata was an Azorean endemic and described a geovicarious taxon in Madeira: F. filiformis C. Sm. ex Link in Buch ssp. mandonii St.-Yves. We undertook a complete bibliographical revision of the taxonomy, nomenclature, and chorology of F. jubata s.l. , and contrasted it with morphological and anatomical studies performed on samples from the Azores and Madeira. Azorean plants usually identified as F. jubata had a character combination distinct from that of those with a Madeiran provenance. Saint-Yves' proposal of two independent taxa was correct, but he erroneously considered F. jubata as an Azorean endemic because the name F. jubata was based on Madeiran plants. Consequently, F. jubata auct. pl. from the Azores belongs to a new species.  © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society , 2008, 157 , 493–499.     

Production of endothelial progenitor cells obtained from human Wharton's jelly using different culture conditions

Endothelial progenitor cells (EPC) participate in revascularization and angiogenesis. EPC can be cultured in vitro from mononuclear cells of peripheral blood, umbilical cord blood or bone marrow; they also can be transdifferentiated from mesenchymal stem cells (MSC). We isolated EPCs from Wharton's jelly (WJ) using two methods. The first method was by obtaining MSC from WJ and characterizing them by flow cytometry and their adipogenic and osteogenic differentiation, then applying endothelial growth differentiating media. The second method was by direct culture of cells derived from WJ into endothelial differentiating media. EPCs were characterized by morphology, Dil-LDL uptake/UEA-1 immunostaining and testing the expression of endothelial markers by flow cytometry and RT-PCR. We found that MSC derived from WJ differentiated into endothelial-like cells using simple culture conditions with endothelium induction agents in the medium.     

Role of external calcium in homeostasis of intracellular pH in the cyanobacterium Anabaena sp. strain PCC7120 exposed to low pH

The role of external Ca²⁺ in the homeostasis of intracellular pH (pHi) of Anabaena sp. strain PCC7120 in response to a decrease in the external pH (pHex) has been studied in cell suspensions. Increase in cytoplasmic pH after acid shock is dependent on the presence of Ca²⁺ in the medium. The observed Ca²⁺-mediated alkalization of the cytoplasm depends on the extent of the shift in external pH. Acid pH shifts resulted in an increased permeability of the cytoplasmic membrane to protons, which could be reversed by increasing the concentration of Ca²⁺ in the medium. Thus, the ability of Ca²⁺ to increase cytoplasmic pH might be correlated with an inhibition of net proton uptake by increasing concentrations of external Ca²⁺ under these conditions. This combined response resulted in the generation and maintenance of a larger pH gradient (ΔpH) at acid external pH values. All Ca²⁺ channel blockers tested, such as verapamil and LaCl₃, inhibited the observed Ca²⁺-mediated response. On the other hand, the Ca ionophore calcimycin (compound A23187) was agonistic, and stimulated both cytoplasmic alkalization and inhibition of net proton uptake. The protonophorous uncoupler carbonylcyanide m -chlorophenyl hydrazone, inhibited this Ca²⁺-mediated response, whereas monensin, an inhibitor of the Na⁺/H⁺ antiporter, had no significant effect. The results of the present study suggest that an influx of Ca²⁺ from the extracellular space is required for the regulation of cytoplasmic pH in Anabaena sp. strain PCC7120 exposed to low external pH values.