An experimental study of foam-oil interactions for nonionic-based binary surfactant systems under high salinity conditions.

A key factor affecting foam stability is the interaction of foam with oil in the reservoir. This work investigates how different types of oil influence the stability of foams generated with binary surfactant systems under a high salinity condition. Foam was generated with binary surfactant systems, one composed of a zwitterionic and a nonionic surfactant, and the other composed of an anionic and a nonionic surfactant. Our results showed that the binary surfactant foams investigated are more tolerant under high salinity conditions and in the presence of oil. This was visually observed in our microscopic analysis and was further attributed to an increase in apparent viscosity achieved with binary surfactant systems, compared to single surfactant foams. To understand the influence of oil on foam stability, we performed a mechanistic study to investigate how these oils interact with foams generated with binary surfactants, focusing on their applicability under high salinity conditions. The generation and stability of foam are linked to the ability of the surfactant system to solubilize oil molecules. Oil droplets that solubilize in the micelles appear to destabilize the foam. However, oils with higher molecular weights are too large to be solubilized in the micelles, hence the molecules will have less ability to be transported out of the foam, so oil seems to stabilize the foam. Finally, we conducted a multivariate analysis to identify the parameters that influenced foam stability in different oil types, using the experimental data from our work. The results showed that the oil molecular weight, interfacial tension between the foaming liquid and the oil, and the spreading coefficient are the most important variables for explaining the variation in the data. By performing a partial least square regression, a linear model was developed based on these most important variables, which can be used to predict foam stability for subsequent experiments under the same conditions as our work.

Genome Variability in Artificial Allopolyploid Hybrids of Avena sativa L. and Avena macrostachya Balansa ex Coss. et Durieu Based on Marker Sequences of Satellite DNA and the ITS1-5.8S rDNA Region.

Artificial hybrids between cultivated Avena species and wild Avena macrostachya that possess genes for resistance to biotic and abiotic stresses can be important for oat breeding. For the first time, a comprehensive study of genomes of artificial fertile hybrids Avena sativa × Avena macrostachya and their parental species was carried out based on the chromosome FISH mapping of satellite DNA sequences (satDNAs) and also analysis of intragenomic polymorphism in the 18S-ITS1-5.8S rDNA region, using NGS data. Chromosome distribution patterns of marker satDNAs allowed us to identify all chromosomes in the studied karyotypes, determine their subgenomic affiliation, and detect several chromosome rearrangements. Based on the obtained cytogenomic data, we revealed differences between two A. macrostachya subgenomes and demonstrated that only one of them was inherited in the studied octoploid hybrids. Ribotype analyses showed that the second major ribotype of A. macrostachya was species-specific and was not represented in rDNA pools of the octoploids, which could be related to the allopolyploid origin of this species. Our results indicate that the use of marker satDNAs in cytogenomic studies can provide important data on genomic relationships within Avena allopolyploid species and hybrids, and also expand the potential for interspecific crosses for breeding.

Hybridization in the Subtribe Alopecurinae Dumort. (Poaceae) According to Molecular Phylogenetic Analysis: Different Ploidy Level Tells Different Origin of the Groups.

We performed next-generation sequencing of the 18S rDNA-ITS1-5.8S rDNA region along with traditional Sanger sequencing of rbcL, matK, ndhF, and ITS1-5.8S rDNA-ITS2 to clarify the hybridization pattern in the subtribe Alopecurinae and in the genus Alopecurus in particular. Our data support the hybrid origin of Alopecurus × brachystylus from hybridization between A. geniculatus (sect. Alopecurium) and A. pratensis (sect. Alopecurus). Moreover, in the rDNA of hybrid A. × brachystylus, only A. aequalis-like ribotypes from tetraploid A. geniculatus participated. Surprisingly, we found the traces of introgression of A. arundinaceus-like ribotypes not only in hybrid A. × marssonii (A. geniculatus × A. arundinaceus) but in A. aequalis s. str. as well. A high-polyploid group from the section Alopecurus, A. aggr. alpinus has undoubted hybrid origin: e. g., A. brachystachyus has rDNA from the sect. Alopecurium. Alopecurus alpinus, with its allies, is clearly distinct from other members of the sect. Alopecurus (especially by maternal line) and thus we can re-establish a previous opinion about the separate group to which A. alpinus belongs. Species from the section Colobachne (presumably Alpine grasses from Ancient Mediterranean region) probably hybridized with the A. alpinus group. Even A. myosuroides (sect. Pseudophalaris) that could be referred to the separate genus has ribotypes common with the species of the section Alopecurium (A. aequalis, A. geniculatus) in one of the accessions. Additionally, we found that the possible polyphyletic origin of the genus Limnas. Limnas stelleri is very close to Alopecurus magellanicus according to NGS data, while L. malyschevii is more or less distinct from other studied species of the genus Alopecurus.

Characterization of a HIR-Fab-IDS, Novel Iduronate 2-Sulfatase Fusion Protein for the Treatment of Neuropathic Mucopolysaccharidosis Type II (Hunter Syndrome).

BACKGROUND: Mucopolysaccharidosis type II is a severe lysosomal storage disease caused by deficient activity of the enzyme iduronate-2-sulfatase. The only medicinal product approved by the US Food and Drug Administration for enzyme replacement therapy, recombinant iduronate-2-sulfatase (idursulfase, Elaprase®), is a large molecule that is not able to cross the blood-brain barrier and neutralize progressive damage of the central nervous system caused by the accumulation of glycosaminoglycans. Novel chimeric protein HIR-Fab-IDS is an anti-human insulin receptor Fab fragment fused to recombinant modified iduronate-2-sulfatase. This modification provides a highly selective interaction with the human insulin receptor, which leads to the HIR-Fab-IDS crossing the blood-brain barrier owing to internalization of the hybrid molecule by transcytosis into endothelial cells adjacent to the nervous system by the principle of a 'molecular Trojan horse'. OBJECTIVES: In this work, the physicochemical and biological characterization of a blood-brain barrier-penetrating fusion protein, HIR-Fab-IDS, is carried out. HIR-Fab-IDS consists of an anti-human insulin receptor Fab fragment fused to recombinant iduronate-2-sulfatase. METHODS: Comprehensive analytical characterization utilizing modern techniques (including surface plasmon resonance and mass spectrometry) was performed using preclinical and clinical batches of HIR-Fab-IDS. Critical quality parameters that determine the therapeutic effect of iduronate-2-sulfatase, as well as IDS enzymatic activity and in vitro cell uptake activity were evaluated in comparison with the marketed IDS product Elaprase® (IDS RP). In vivo efficiency of HIR-Fab-IDS in reversing mucopolysaccharidosis type II pathology in IDS-deficient mice was also investigated. The affinity of the chimeric molecule for the INSR was also determined by both an enzyme-linked immunosorbent assay and surface plasmon resonance. We also compared the distribution of 125I-radiolabeled HIR-Fab-IDS and IDS RP in the tissues and brain of cynomolgus monkeys after intravenous administration. RESULTS: The HIR-Fab-IDS primary structure investigation showed no significant post-translational modifications that could affect IDS activity, except for the formylglycine content, which was significantly higher for HIR-Fab-IDS compared with that for IDS RP (~ 76.5 vs ~ 67.7%). Because of this fact, the specific enzyme activity of HIR-Fab-IDS was slightly higher than that of IDS RP (~ 2.73 × 106 U/µmol vs ~ 2.16 × 106 U/µmol). However, differences were found in the glycosylation patterns of the compared IDS products, causing a minor reduced in vitro cellular uptake of HIR-Fab-IDS by mucopolysaccharidosis type II fibroblasts compared with IDS RP (half-maximal effective concentration ~ 26.0 vs ~ 23.0 nM). The efficacy of HIR-Fab-IDS in IDS-deficient mice has demonstrated a statistically significant reduction in the level of glycosaminoglycans in the urine and tissues of the main organs to the level of healthy animals. The HIR-Fab-IDS has revealed high in vitro affinity for human and monkey insulin receptors, and the radioactively labeled product has been shown to penetrate to all parts of the brain and peripheral tissues after intravenous administration to cynomolgus monkeys. CONCLUSIONS: These findings indicate that HIR-Fab-IDS, a novel iduronate-2-sulfatase fusion protein, is a promising candidate for the treatment of central nervous system manifestations in neurological mucopolysaccharidosis type II.

Kinetics and Mechanism of Liquid-State Polymerization of 2,4-Hexadiyne-1,6-diyl bis-(p-toluenesulfonate) as Studied by Thermal Analysis.

A detailed investigation of the liquid-state polymerization of diacetylenes by calorimetric (DSC) and spectroscopic (in situ EPR) thermal analysis techniques is performed. Isoconversional kinetic analysis of the calorimetric data reveals that liquid-state polymerization is governed by a well-defined rate-limiting step as evidenced by a nearly constant isoconversional activation energy. By comparison, solid-state polymerization demonstrates isoconversional activation energy that varies widely, signifying multistep kinetics behavior. Unlike the solid-state reaction that demonstrates an autocatalytic behavior, liquid-state polymerization follows a rather unusual zero-order reaction model as established by both DSC and EPR data. Both techniques have also determined strikingly similar Arrhenius parameters for liquid-state polymerization. Relative to the solid-state process, liquid-state polymerization results in quantitative elimination of the p-toluenesulfonate group and the formation of p-toluenesulfonic acid and a polymeric product of markedly different chemical and phase composition.

Diversity of Arbuscular Mycorrhizal Fungi in Distinct Ecosystems of the North Caucasus, a Temperate Biodiversity Hotspot.

BACKGROUND: Investigations that are focused on arbuscular mycorrhizal fungus (AMF) biodiversity is still limited. The analysis of the AMF taxa in the North Caucasus, a temperate biodiversity hotspot, used to be limited to the genus level. This study aimed to define the AMF biodiversity at the species level in the North Caucasus biotopes. METHODS: The molecular genetic identification of fungi was carried out with ITS1 and ITS2 regions as barcodes via sequencing using Illumina MiSeq, the analysis of phylogenetic trees for individual genera, and searches for operational taxonomic units (OTUs) with identification at the species level. Sequences from MaarjAM and NCBI GenBank were used as references. RESULTS: We analyzed >10 million reads in soil samples for three biotopes to estimate fungal biodiversity. Briefly, 50 AMF species belonging to 20 genera were registered. The total number of the AM fungus OTUs for the "Subalpine Meadow" biotope was 171/131, that for "Forest" was 117/60, and that for "River Valley" was 296/221 based on ITS1/ITS2 data. The total number of the AM fungus species (except for virtual taxa) for the "Subalpine Meadow" biotope was 24/19, that for "Forest" was 22/13, and that for "River Valley" was 28/24 based on ITS1/ITS2 data. Greater AMF diversity, as well as number of OTUs and species, in comparison with that of forest biotopes, characterized valley biotopes (disturbed ecosystems; grasslands). The correlation coefficient between "Percentage of annual plants" and "Glomeromycota total reads" r = 0.76 and 0.81 for ITS1 and ITS2, respectively, and the correlation coefficient between "Percentage of annual plants" and "OTUs number (for total species)" was r = 0.67 and 0.77 for ITS1 and ITS2, respectively. CONCLUSION: High AMF biodiversity for the river valley can be associated with a higher percentage of annual plants in these biotopes and the active development of restorative successional processes.

Origin of the Rare Hybrid Genus ×Trisetokoeleria Tzvelev (Poaceae) According to Molecular Phylogenetic Data.

In our article, we analyzed new data on the origin of the hybrid genus ×Trisetokoeleria. According to the morphological criteria ×T. jurtzevii is a hybrid between Koeleria asiatica s. l. and Trisetum spicatum, ×T. taimyrica, and originated from Koeleria asiatica s. l. and Trisetum subalpestre, ×T. gorodkowii, a hybrid between Koeleria asiatica and Trisetum ruprechtianum. Later ×T. taimyrica was transferred to Koeleria. Parental taxa are prone to active hybridization themselves, thus, new methods of next-generation sequencing (NGS) were needed to clarify the relationships of these genera. For NGS we used the fragment 18S rDNA (part)-ITS1-5.8S rDNA (totally 441 accessions). We analyzed ITS1-5.8S rDNA-ITS2 region, trnL-trnF and trnK-rps16 from eight samples of the five species, using the Sanger method: ×Trisetokoeleria jurtzevii, ×T. taimyrica, Koeleria asiatica, Sibirotrisetum sibiricum (=Trisetum sibiricum), and Trisetum spicatum. We also studied the pollen fertility of ×Trisetokoeleria and its possible progenitors. Our data partly contradicted previous assumptions, based on morphological grounds, and showed us a picture of developed introgression within and between Koeleria and Trisetum. ×T. jurtzevii, a totally sterile hybrid formed rather recently. We can suppose that ×T. jurtzevii is a hybrid between K. asiatica and some Trisetum s. str. Species, but not T. spicatum. ×T. gorodkowii, a hybrid in the stage of primary stabilization; it has one unique ribotype related to T. spicatum s. l. The second parental species is unrelated to Trisetum ruprechtianum. ×T. taimyrica and is a stabilized hybrid species; it shares major ribotypes with the T. spicatum/T. wrangelense group and has a minor fraction of rDNA related to genus Deyeuxia s. l.

Computationally Efficient Concept of Representative Directions for Anisotropic Fibrous Materials.

The concept of representative directions allows for automatic generation of multi-axial constitutive equations, starting from simplified uni-axial material models. In this paper, a modification of the concept is considered suitable for the analysis of fibrous polymeric materials, which are anisotropic in the as-received state. The modification of the concept incorporates an orientation probability density function (OPDF), which explicitly accounts for the material anisotropy. Two versions of the concept are available. The first version utilizes the homogeneous distribution of the representative directions, with the entire anisotropy being contained in the weighting factors. The second encapsulates the anisotropy in the distribution of the representative directions. Due to its nature, the second version allows for a more efficient use of computational power. To promote this efficient version of the concept, we present new algorithms generating required sets of representative directions that match a given OPDF. These methods are based (i) on the minimization of a potential energy, (ii) on the equilibration method, and (iii) on the use of Voronoi cells. These three methods are tested and compared in terms of various OPDFs. The applicability of the computationally efficient modeling method to mechanical behavior of an anisotropic polymeric material is demonstrated. In particular, a calibration procedure is suggested for the practically important case when the OPDF is not known a-priori.

New Insights into the Genomic Structure of Avena L.: Comparison of the Divergence of A-Genome and One C-Genome Oat Species.

We used next-generation sequencing analysis of the 3'-part of 18S rDNA, ITS1, and a 5'-part of the 5.8S rDNA region to understand genetic variation among seven diploid A-genome Avena species. We used 4−49 accessions per species that represented the As genome (A. atlantica, A. hirtula, and wiestii), Ac genome (A. canariensis), Ad genome (A. damascena), Al genome (A. longiglumis), and Ap genome (A. prostrata). We also took into our analysis one C-genome species, A. clauda, which previously was found to be related to A-genome species. The sequences of 169 accessions revealed 156 haplotypes of which seven haplotypes were shared by two to five species. We found 16 ribotypes that consisted of a unique sequence with a characteristic pattern of single nucleotide polymorphisms and deletions. The number of ribotypes per species varied from one in A. longiglumis to four in A. wiestii. Although most ribotypes were species-specific, we found two ribotypes shared by three species (one for A. damascena, A. hirtula, and A. wiestii, and the second for A. longiglumis, A. atlantica, and A. wiestii), and a third ribotype shared between A. atlantica and A. wiestii. A characteristic feature of the A. clauda ribotype, a diploid C-genome species, is that two different families of ribotypes have been found in this species. Some of these ribotypes are characteristic of Cc-genome species, whereas others are closely related to As-genome ribotypes. This means that A. clauda can be a hybrid between As- and C-genome oats.

Analysis of the Osseointegration Process of Dental Implants by Electron Paramagnetic Resonance: An In Vivo Study.

This research work presents an analysis of the process of an implant's osseointegration to the jawbone tissue. The purpose of this work was to describe the processes of assimilation and the biochemical dynamics which occur during dental implantation using implants with different macro-microstructure surfaces at the level of stable free radicals using the electron paramagnetic resonance (EPR) method. The experimental investigation was conducted on seven Vietnamese minipigs over twelve months old and weighing up to 30 kg using implants with various macro-microstructure surfaces (SLA, RBM, and HSTTM) and implantation systems, namely the Adin, Sunran, Biomed, and Osstem systems. The integration of the implant into the bone triggered biochemical processes with the formation of stable free radicals. The EPR method was used to identify the formed paramagnetic species and to study the dynamics of the interaction between the surface of the implant and the bone after one and two months. The concentration of carbonate surface centers increased with the time that the implant was connected to the hard tissue. The "Sunran" and "HSTTM" were established as the most suitable implantation system and surface type, respectively, thanks to the highest rate of osseointegration (assimilation) with the bone (hard) tissue. Thus, the EPR method provides the opportunity to study implantation processes.

Correction: Rodionov, A.V., et al. Intragenomic Polymorphism of the ITS 1 Region of 35S rRNA Gene in the Group of Grasses with Two-Chromosome Species: Different Genome Composition in Closely Related Zingeria Species. Plants 2020, 9, 1647.

The authors wish to make the following corrections to their paper [...].

Metallo-Supramolecular Coordination Polymers Based on Amidopyridine Derivatives of Pillar[5]arene and Cu(II) and Pd(II) Cations: Synthesis and Recognition of Nitroaromatic Compounds.

Decasubstituted pillar[5]arenes containing amidopyridine fragments have been synthesized for the first time. As was shown by UV-vis spectroscopy, the pillar[5]arenes with p-amidopyridine fragments form supramolecular associates with Cu(II) and Pd(II) cations in methanol in a 2:1 ratio. Using a sol-gel approach these associates are transformed into metallo-supramolecular coordination polymers (supramolecular gels) which were characterized as amorphous powders by scanning electron microscopy (SEM) and dynamic light scattering (DLS). The powders are able to selectively adsorb up to 46% of nitrophenols from water and were incorporated into an electrochemical sensor to selectively recognize them in aqueous acidic solution.

Intragenomic Polymorphism of the ITS 1 Region of 35S rRNA Gene in the Group of Grasses with Two-Chromosome Species: Different Genome Composition in Closely Related Zingeria Species.

Zingeria (Poaceae) is a small genus that includes Z. biebersteiniana, a diploid species with the lowest chromosome number known in plants (2n = 4) as well as hexaploid Z. kochii and tetraploid Z. pisidica, and/or Z. trichopoda species. The relationship between these species and the other low-chromosomes species Colpodium versicolor are unclear. To explore the intragenomic polymorphism and genome composition of these species we examined the sequences of the internal transcribed spacer 1 of the 35S rRNA gene via NGS approach. Our study revealed six groups of ribotypes in Zingeria species. Their distribution confirmed the allopolyploid nature of Z. kochii, whose probable ancestors were Colpodium versicolor and Z. pisidica. Z. pisidica has 98% of rDNA characteristic only for this species, and about 0.3% of rDNA related to that of Z. biebersteiniana. We assume that hexaploid Z. kochii is either an old allopolyploid or a homodiploid that has lost most of the rRNA genes obtained from Z. biebersteiniana. In Z. trichopoda about 81% of rDNA is related to rDNA of Z. biebersteiniana and 19% of rDNA is derived from Poa diaphora sensu lato. The composition of the ribotypes of the two plants determined by a taxonomy specialist as Z. pisidica and Z. trichopoda is very different. Two singleton species are proposed on this base with ribotypes as discriminative characters. So, in all four studied Zingeria species, even if the morphological difference among the studied species was modest, the genomic constitution was significantly different, which suggests that these are allopolyploids that obtained genomes from different ancestors.

Determination and correction of aberrations in full field optical coherence tomography using phase gradient autofocus by maximizing the likelihood function.

A method for numerical estimation and correction of aberrations of the eye in fundus imaging with optical coherence tomography (OCT) is presented. Aberrations are determined statistically by using the estimate based on likelihood function maximization. The method can be considered as an extension of the phase gradient autofocusing algorithm in synthetic aperture radar imaging to 2D optical aberration correction. The efficacy of the proposed method has been demonstrated in OCT fundus imaging with 6λ aberrations. After correction, single photoreceptors were resolved. It is also shown that wave front distortions with high spatial frequencies can be determined and corrected.

Molecular cytogenetics of valuable Arctic and sub-Arctic pasture grass species from the Aveneae/Poeae tribe complex (Poaceae).

BACKGROUND: Grasslands in the Arctic tundra undergo irreversible degradation due to climatic changes and also over-exploitation and depletion of scarce resources. Comprehensive investigations of cytogenomic structures of valuable Arctic and sub-Arctic grassland species is essential for clarifying their genetic peculiarities and phylogenetic relationships, and also successful developing new forage grass cultivars with high levels of adaptation, stable productivity and longevity. We performed molecular cytogenetic characterization of insufficiently studied pasture grass species (Poaceae) from related genera representing two neighboring clades: 1) Deschampsia and Holcus; 2) Alopecurus, Arctagrostis and Beckmannia, which are the primary fodder resources in the Arctic tundra. RESULTS: We constructed the integrated schematic maps of distribution of these species in the northern, central and eastern parts of Eurasia based on the currently available data as only scattered data on their occurrence is currently available. The species karyotypes were examined with the use of DAPI-banding, multicolour FISH with 35S rDNA, 5S rDNA and the (GTT)9 microsatellite motif and also sequential rapid multocolour GISH with genomic DNAs of Deschampsia sukatschewii, Deschampsia flexuosa and Holcus lanatus belonging to one of the studied clades. Cytogenomic structures of the species were specified; peculiarities and common features of their genomes were revealed. Different chromosomal rearrangements were detected in Beckmannia syzigachne, Deschampsia cespitosa and D. flexuosa; B chromosomes with distinct DAPI-bands were observed in karyotypes of D. cespitosa and H. lanatus. CONCLUSIONS: The peculiarities of distribution patterns of the examined chromosomal markers and also presence of common homologous DNA repeats in karyotypes of the studies species allowed us to verify their relationships. The obtained unique data on distribution areas and cytogenomic structures of the valuable Arctic and sub-Arctic pasture species are important for further genetic and biotechnological studies and also plant breeding progress.

Improvement of vibrodamping properties of polyvinyl acetate-graphite composites by electron beam processing of the filler.

The effect of electron beam processing (energy 900 keV, absorbed dose in the range from 25 to 600 kGy) of graphite upon the efficiency of its use as a filler in polyvinyl acetate (PVA) based vibrodamping composites is studied. Graphite treatment at optimal doses above 200 kGy is found to provide a significant increase of damping loss factor for these composites at ambient and especially at elevated temperatures. The observed improvement of vibrodamping properties correlates with the increase in the content of Broensted centers (hydroxyl groups) on modified graphite surface probably due to the additional bonding of the filler particles with each other and PVA binder.

Fe(III) mineral reduction followed by partial dissolution and reactive oxygen species generation during 2,4,6-trinitrotoluene transformation by the aerobic yeast Yarrowia lipolytica.

Understanding the factors that influence pollutant transformation in the presence of ferric (oxyhydr)oxides is crucial to the efficient application of different remediation strategies. In this study we determined the effect of goethite, hematite, magnetite and ferrihydrite on the transformation of 2,4,6-trinitrotoluene (TNT) by Yarrowia lipolytica AN-L15. The presence of ferric (oxyhydr)oxides led to a small decrease in the rate of TNT removal. In all cases, a significant release of NO2 (-) from TNT and further NO2 (-) oxidation to NO3 (-) was observed. A fraction of the released NO2 (-) was abiotically decomposed to NO and NO2, and then NO was likely oxidized abiotically to NO2 by O2. ESR analysis revealed the generation of superoxide in the culture medium; its further protonation at low pH resulted in the formation of hydroperoxyl radical. Presumably, a fraction of NO released during TNT degradation reacted with superoxide and formed peroxynitrite, which was further rearranged to NO3 (-) at the acidic pH values observed in this study. A transformation and reduction of ferric (oxyhydr)oxides followed by partial dissolution (in the range of 7-86% of the initial Fe(III)) were observed in the presence of cells and TNT. Mössbauer spectroscopy showed some minor changes for goethite, magnetite and ferrihydrite samples during their incubation with Y. lipolytica and TNT. This study shows that i) reactive oxygen and nitrogen species generated during TNT transformation by Y. lipolytica participate in the abiotic conversion of TNT and ii) the presence of iron(III) minerals leads to a minor decrease in TNT transformation.

FISH on avian lampbrush chromosomes produces higher resolution gene mapping.

Giant lampbrush chromosomes, which are characteristic of the diplotene stage of prophase I during avian oogenesis, represent a very promising system for precise physical gene mapping. We applied 35 chicken BAC and 4 PAC clones to both mitotic metaphase chromosomes and meiotic lampbrush chromosomes of chicken (Gallus gallus domesticus) and Japanese quail (Coturnix coturnix japonica). Fluorescence in situ hybridization (FISH) mapping on lampbrush chromosomes allowed us to distinguish closely located probes and revealed gene order more precisely. Our data extended the data earlier obtained using FISH to chicken and quail metaphase chromosomes 1-6 and Z. Extremely low levels of inter- and intra-chromosomal rearrangements in the chicken and Japanese quail were demonstrated again. Moreover, we did not confirm the presence of a pericentric inversion in Japanese quail chromosome 4 as compared to chicken chromosome 4. Twelve BAC clones specific for chicken chromosome 4p and 4q showed the same order in quail as in chicken when FISH was performed on lampbrush chromosomes. The centromeres of chicken and quail chromosomes 4 seem to have formed independently after centric fusion of ancestral chromosome 4 and a microchromosome.

Interstitial (TTAGGG)(n) sequences are not hot spots of recombination in the chicken lampbrush macrochromosomes 1-3.

To study the role of telomere (TTAGGG)(n) sequences in promoting of crossing over in chicken female meiosis, we have localized telomere repeats by FISH and studied the distribution of chiasmata in the giant diplotene bivalents, the chicken lampbrush macrochromosomes 1--3. We show that all interstitial clusters of the (TTAGGG)(n) repeat in these chromosomes do not coincide with hot spots of genetic recombination (crossing over) in the chicken female. Moreover, terminal TTAGGG-positive chromomeres also are not chiasma hot spots. We conclude that, at least in chicken macrochromosomes in female meiosis, a role for canonical telomere sequences in promoting of crossing over is not confirmed.