bluuebunny/crossref_metadata_2025_split huggingface dataset:
Late Pleistocene glacial geomorphology and environment of the Hand Hills region and southern Alberta, related to Middle Wisconsin fossil prairie dog sites
Authors: Young R R , Burns J A , Rains R B , Schowalter D B 
Published: April 2011

Ichnofossils (burrow casts) and fossils from an extinct form of prairie dog, Cynomys niobrarius churcherii, in the Hand Hills of south-central Alberta, have provided an important Late Pleistocene stratigraphic marker. The marker fossils provide relative and chronostratigraphic (radiocarbon) ages for nonglacial, periglacial, glacial, and glaciotectonic events and environments in the region. The high-elevation, hilltop position of the fossil sites (~200 m above the surrounding plains) permits reliable extrapolations of glacial environments to the surrounding region. The burrow casts were preserved by infilling from surrounding and overlying sediments through processes of inwashing and animal activity. Three thousand bones, primarily of the extinct prairie dog Cynomys niobrarius churcherii, were recovered from one site, and several hundred more from other locations. Accelerator radiocarbon dates (AMS) on bone collagen show that the prairie dogs lived in the area from at least 33 000 BP to around 22 000 BP. Prairie dog burrow casts crosscut well-developed periglacial structures and stratigraphically underlie all glacial sediments, indicating that harsh periglacial environments preceded their colonization and that the region was later submerged by Laurentide ice. Deformed sediments, 0.5 to 1.5 m thick, were found throughout the upland. The products of deformation overlie, truncate, and (or) incorporate burrow casts, indicating that only limited erosion and glacial deformation occurred during glaciation. Reconstructed ice sheet profiles show a northwest-southeast flow that could only have been achieved by coalescent Laurentide and Cordilleran ice sheets. This demonstrates that a theoretical "ice-free corridor" that some think persisted between the ice sheets during the Late Wisconsin "maximum," did not exist.
Karyotype polymorphism in Drosophila albomicans
Authors: Hatsumi Machiko 
Published: April 2011

Supernumerary (B) chromosomes are present in Thai, Malay, and Burmese populations of Drosophila albomicans (2n = 6) in a polymorphic state. Although usually stable at mitosis, their numbers differed between individuals and their frequency was also different between isofemale lines and between populations. Arm 3 of the X3 chromosome was polymorphic for the presence and the size of a procentric heterochromatic segment. Chromosome 4 is polytypic for variation in length governed by differences in the amount of heterochromatin and the long variant is polymorphic for the location of its secondary constriction. Key words: Drosophila albomicans, karyotype polymorphism, B chromosome.
Relative stability among barley plants regenerated from cultured immature embryos
Authors: Karp A. , Steele S. H. , Parmar S. , Jones M. G. K. , Shewry P. R. , Breiman A. 
Published: April 2011

Relative genetic stability was observed among barley plants regenerated from cultured immature embryos. Regenerated plants were studied cytologically and their seed progenies assayed for (i) the isoenzymes esterase and glutamate-oxaloacetate transaminase, (ii) ribosomal DNA spacer length polymorphism, and (iii) hordein patterns on SDS–PAGE. Of 42 regenerated plants, 1 regenerant had abnormal meiosis and the same plant produced one seed with a variant hordein pattern. These findings are discussed in relation to the factors affecting somaclonal variation in cereals and to methods of assaying the variation. Key words: barley, isozymes, somaclonal variation, tissue culture.
Possible role of heterochromatin in chromosome breakage induced by tissue culture in oats (Avena sativa L.)
Authors: Johnson S. S. , Phillips R. L. , Rines H. W. 
Published: April 2011

Perturbations in the replication of heterochromatic regions during tissue culture may be the cause of chromosome alterations observed in regenerated hexaploid oat plants (Avena sativa L.). An idiogram based on pachytene chromosome analysis was developed depicting the heterochromatin distribution on 17 of the 21 chromosomes. Heterochromatic regions were present pericentromerically on each chromosome, at telomeres in five of the chromosomes, and in the NORs of the three satellited chromosomes. Centromeric heterochromatin covered most of the short arm in several chromosomes. Tritiated-thymidine autoradiography was used to determine the nuclear cycle duration (G1 + S + G2 + mitosis = 0.8 + 5.2 + 0.3 + 3.8h = 10.1 h) in root-tip cells and revealed regions of late replication around the primary and secondary constrictions and at chromosome ends. Replication of heterochromatic regions late in the DNA synthetic period makes it plausible that these regions are more sensitive to nuclear cycle alterations caused by the culture process. Pachytene analysis of a heteromorphic chromosome pair that originated during culture showed the break in the deficient chromosome to be in centromeric heterochromatin. The presence of proximal and telomeric heterochromatin means that bridges resulting from replication problems in these regions could result in various alterations including deficiencies, duplications, and translocations and can account for heterochromatin amplification, all of which have been observed in plants that have been regenerated from tissue culture. Key words: heterochromatin, meiosis, telocentric chromosomes, oats, tissue culture, variation.
Breeding foxtail millet (Setaria italica) for quantitative traits after interspecific hybridization and polyploidization
Authors: Darmency H. , Ouin C. , Pernes J. 
Published: April 2011

An interspecific cross was carried out between the cultivated foxtail millet, Setaria italica, and its wild relative the green foxtail, S. viridis. Quantitative characters (19 descriptors of morphology and reproduction) were studied using the F1 F2, and F3 generations. Moreover, this F2 was compared with the tetraploid F2 obtained from a colchicine-induced F1. The multivariate analysis of the diploid F2 showed two complex associations of characters: one concerning developmental traits (organs dimensions and flowering) and the other dealing with taxonomical characteristics (tillering, seed shedding, and seed weight). The tetraploidization resulted in a shift in characteristics towards the crop species, especially a twofold increase in seed weight. Nonadditive effects were found for most characters, except for the seed shedding, which was found to be encoded by at least four loci. However, cultivated type plants were easily recovered in both the diploid and the tetraploid F2. This demonstrates the potential of interspecific hybridization and polyploidization to improve the crop properties of the foxtail millet. Key words: foxtail millet, polyploid, quantitative inheritance, hybridization (interspecific).
Polyploid complexes of Glycine tabacina (Labill.) Benth. and G. tomentella Hayata revealed by cytogenetic analysis
Authors: Singh R. J. , Kollipara K. P. , Hymowitz T. 
Published: April 2011

Observations on geographical distribution, cytotypes, crossability, and meiotic chromosome behavior in intra- and interspecific F1 hybrids revealed that the complexes of Glycine tabacina (2n = 40, 80) and G. tomentella (2n = 38, 40, 78, 80) evolved through allopolyploidization. It is apparent from this study that 80-chromosome tabacinas are composed of two distinct morphological complexes having one common genome: with and without adventitious roots. In contrast, the tomentellas are inseparable morphologically. They are composed of accessions with at least three genomic complexes: (i) 2n = 80, accessions from Australia and Taiwan; (ii) 2n = 80, an accession from Papua New Guinea; and (iii) 2n = 78, accessions from Australia and Papua New Guinea. Hybrids within each group showed complete synapsis and set normal seeds; however, hybrids between the groups apparently differed by one genome and were completely sterile. Chromosome pairing in triploid interspecific F1 hybrids (2n = 59, 60) indicated that G. canescens (2n = 40) was probably the donor of the common genome for 80-chromosome tabacinas and tomentellas. Glycine latifolia (2n = 40) appears to have contributed its genome to G. tabacina (2n = 80) but could not have participated in the speciation of 80-chromosome tomentellas. Likewise, the 38-chromosome G. tomentella has no genomic affinity with 80-chromosome tabacinas but has complete affinity with 80-chromosome tomentellas. On the basis of present findings and the results published earlier, the evolution of the genus Glycine will be discussed. Key words: Glycine spp., genome, hybridization (intraspecific), hybridization (interspecific), speciation.
Unusual germ line limited chromosomes in Acricotopus lucidus (Diptera, Chironomidae)
Authors: Staiber W. 
Published: April 2011

A small supernumerary polytene chromosome was found during the last 8 years in some rare cases in larval salivary gland cells of Acricotopus lucidus (Diptera, Chironomidae). The chromosome may be derived from the germ line restricted parts of the genome. It consists of a short heterochromatic segment and of euchromatic sections with banding patterns homologous to sections of the short arm of soma chromosome I. When examining male meiosis, an exceptional small germ line limited chromosome was found. It is believed that this chromosome was not always recognized during soma elimination as a germ line limited chromosome, probably because of its partial homology to one of the soma chromosomes, and was then polytenized in salivary gland cells. Another germ line limited chromosome with a characteristic morphology and with a special behavior in differential gonial mitosis was found to have existed for more than 12 years in a laboratory stock. In differential gonial mitosis this special germ line limited chromosome partly pairs with the long arm of soma chromosome I. The present results strongly support the idea that the germ line limited chromosomes of A. lucidus are derived from the soma chromosomes, and show that chromosomes of the germ line restricted part of the genome can persist for many generations in a laboratory stock in spite of complex chromosome elimination mechanisms in the primary germ cells. Key words: germ line limited chromosomes, supernumerary polytene chromosome, salivary gland, Acricotopus lucidus.
Detection of the time of occurrence of nondisjunction induced by the r-X1 deficiency in Zea mays L.
Authors: Simcox Kevin D. , Shadley Jeffery D. , Weber David F. 
Published: April 2011

The r-X1 deficiency in maize produces high frequencies of aneuploid progeny by inducing nondisjunction during embryo sac development. The purpose of this investigation was to determine the embryo sac division at which the nondisjunctive event takes place. Monosomic-6 individuals were generated by crossing r-X1 containing plants by those carrying the y-pastel-8549 allele of the Y locus on chromosome 6. A strict dosage relationship exists between the number of dominant alleles of the Y locus and the level of β-carotene in the endosperm. We found that the level of β-carotene in the endosperm of kernels containing monosomic-6 embryos was comparable with that found in endosperms with one Y allele. This indicated that they contained only one maternally contributed chromosome 6. Only nondisjunction at the second postmeiotic division could have produced such an endosperm; thus, the nondisjunctive event occurs at this division. Another endosperm type expected from nondisjunction at this same division, with three dominant Y alleles, was not found. The absence of this endosperm type suggests that the egg nucleus and the polar nucleus originating at the micropylar pole are sister nuclei that arose from the same cell at the third embryo sac mitotic division. Key words: aneuploidy, embryo sac, nondisjunction, r-X1 deficiency, Zea.
A revised map of chromosome 16 in Gossypium hirsutum
Authors: Menzel Margaret Y. , Richmond Kenneth L. , Dougherty Brian J. 
Published: April 2011

Four translocations involving chromosome 16 (H16) in cotton (T1R;16R 2770, T1R;16R 4672, T15L;16R 8-5Ga, and T15R;16R 2767) were tested against telosomes for chromosome 16 and the H16 marker gene red plant (R1). The telosome tests confirmed that bp-2770 and bp-4672 are in the long (=right) arm of chromosome 16 and showed that bp-8-5Ga and bp-2767 are also in the long arm of H16, rather than in the short (=left) arm as previously reported. The locations of the chromosome 15 (H15) bp's for 8-5Ga and 2767 are also revised. A telosome test showed that H15 bp-8-5Ga is in the long (=left) arm. Consequently, H15 bp-2767 is placed in the short (=right) arm of chromosome 15. Duplication deficiencies mono- or tri-segmental for H16 (verified cytologically) showed that R1 is in the right (R) arm 24 cM distal to bp-2767 and 10 cM distal to bp-8-5Ga. Recombination frequencies showed that R1 is 13 cM from bp-4672 and 15 cM from bp-2770 (not significantly different). However, both of the T1R;16R translocations yield negligible frequencies of duplication deficiencies and therefore offered no direct evidence as to whether their breakpoints are proximal or distal to R1. Previous estimates have placed both bp-2770 and bp-4672 43 cM from the centromere. Therefore the order must be as follows: (left)–centromere–bp-2767-bp-8-5Ga–R1–bp-4672/bp-2770 (right). Key words: cotton, Gossypium hirsutum, chromosome 16, translocations, linkage map, duplication-deficiences, red plant, linkage group III.
Genetic variation in survival of chinook salmon (Oncorhynchus tshawytscha) alevins exposed to an unidentified agent of mortality
Authors: Withler R. E. 
Published: April 2011

Mortality of an unknown etiology occurs after hatching and before emergence among Harrison River chinook salmon (Oncorhynchus tshawytscha) alevins incubated in the Chehalis River Hatchery, British Columbia. Inter- and intra-stock genetic variation for alevin survival and time to death was investigated at Chehalis Hatchery in factorial crosses among chinook salmon from the Harrison and Capilano rivers. Alevin survival by family ranged from 0 to 100%, with a mean value of 35.2%. The mean family survival of pure Harrison alevins (13.0%) was significantly lower than that of Capilano alevins (64.1%). For the Harrison stock, estimates of the heritability of survival were 1.05 ± 0.62 (sire component) and 0.03 ± 0.07 (dam component). For the Capilano stock, the corresponding estimates were 0.79 ± 0.53 and 0.80 ± 0.54. Family means of time to death ranged from 7.5 to 48 days after exposure to mortality-inducing agents. The mean times to death for pure Harrison (15.3 days) and Capilano (21.8 days) families were not significantly different. Sire and dam component heritability estimates for time to death were high for the Harrison stock (1.39 ± 0.87 and 0.71 ± 0.46) but low for the Capilano stock (0.06 ± 0.11 and 0.17 ± 0.18). Values of survival and time to death for the reciprocal interstock hybrid alevins generally fell between those of the parental stocks. Neither survival nor time to death differed significantly between the reciprocal hybrids, but both traits were more strongly influenced by sire than by dam. The possibility of asynchronous paternal and maternal allele activation during embryonic development was proposed as an explanation for the strong paternal effects observed in this study. Key words: Oncorhynchus, salmon, heritability, mortality.
Cytogenetic analysis of interspecific hybrids between alfalfa (Medicago sativa L.) and M. rhodopea Velen.
Authors: Denton C. R. , McCoy T. J. 
Published: April 2011

Interspecific hybrids between diploid (2n = 2x = 16) Medicago sativa L. and diploid (2n = 2x = 16) M. rhodopea Velen., were recovered using an ovule–embryo culture methodology. Most hybrids were vigorous, and morphological comparisons demonstrated that F1 hybrids were generally intermediate between that of the parents. Peroxidase isozyme phenotypes of the F1 hybrids confirmed hybridity. The chromosome number of most of the hybrids was diploid (2n = 2x = 16), with the exceptions of two triploids (2n = 3x = 24) and two tetraploid (2n = 4x = 32) plants. Chromosome pairing configurations in diploids were almost exclusively eight bivalents or seven bivalents and two univalents, indicating a high level of homology between the M. sativa and M. rhodopea genomes. However, the one triploid hybrid analyzed had only 0.4 trivalents per microspore mother cell indicating preferential pairing of parental genomes. Pollen stainability, pollen germination, and fertility of the diploid F1 hybrid plants were very low; however, it was possible to obtain backcross progeny (BC1) from seed. Pollen stainability, pollen germination, and fertility of the BC1 plants were also very low; however, most BC1 plants had workable levels of male and female fertility. The utilization of M. rhodopea in studies of the evolution of hexaploid Medicago species is discussed. Key words: interspecific hybrids, ovule–embryo culture, isozymes, Medicago.
Arm homoeology of wheat and rye chromosomes
Authors: Naranjo T. , Roca A. , Goicoechea P. G. , Giraldez R. 
Published: April 2011

Meiotic pairing was studied at metaphase I in three different cv. Chinese Spring × rye hybrid combinations (5B deficient, 3D deficient, and normal ABDR) to establish the arm homoeology of wheat and rye chromosomes. The majority of individual wheat chromosomes and their arms, as well as the arms of chromosomes 1R and 5R, were identified by means of C-banding. The results on pairing relationships support the genome reallocation of chromosomes 4A and 4B. The short arms of wheat chromosomes belonging to homoeologous groups 1, 3, 5, and 6 and of chromosome pairs 4A–4D and 7A–7D showed full pairing homoeology as well as the long arms of wheat chromosomes of groups 1, 3, 6, and 7 and of chromosome pairs 4A–4D and 5B–5D. Chromosomes 2A, 2B, and 2D were homoeologous, but the homoeologies of their arms were not identified. Reduced homoeologies of the 4BL arm to 7AS and 7DS, of the 5AL arm to 4AL and 4DL, and of the 7BS arm to 5BL and 5DL were identified. Arms 4BL, 5AL, and 7BS are involved in a double translocation that arose during the evolution of common wheat. The homoeology relationships of chromosome arm 4BS were not identified since this arm seldom paired. The homoeologous pairing pattern between wheat chromosomes was characterized by a remarkable predominance of A–D associations, altered only by structural changes in groups 4 and 5. Chromosome arm 1RL showed full pairing homoeology to 1AL, 1BL, and 1DL, while 5RL was homoeologous to 5AL and partially homoeologous to 4AL and 4DL. It is concluded that 5RL carries a translocated segment from 4RL. Key words: homoeologous pairing, translocations, wheat evolution, C-banding.
Differences in meiotic pairing induction between the A genomes of Triticum boeoticum Boiss. and T. urartu Tum. using diploid species of the subtribe Triticineae as analysers
Authors: Lucas H. , Jahier J. 
Published: April 2011

The number of associations between chromosome arms in the pollen mother cells of the hybrid Triticum boeoticum × T. urartu is similar to that in the pollen mother cells of the parental accessions. The latter two species were crossed with the following diploid species: T. tauschii, T. comosum, T. umbellulatum, and Haynaldia villosa. The meiotic behaviour of the hybrids showed that the chromosomes of T. urartu share more homology with the diploid Triticum species than do those of T. boeoticum. On the other hand, there is more pairing in the hybrid T. boeoticum × H. villosa than in T. urartu × H. villosa. These results confirm that T. boeoticum and T. urartu are distinct species. Key words: Triticineae, interspecific hybrids, meiotic behaviour, speciation.
Novel α4-integrin ligands on an endothelial cell line
Authors: Tudor Kim-Sue RS , Deem Tracy L , Cook-Mills Joan M 
Published: April 2011

The unique combination of adhesion molecules expressed on endothelial cells is thought to mediate the specificity of leukocyte-endothelial cell interactions. In this study, murine endothelial cell lines were used as a model to identify novel adhesion molecules that participate in these cellular interactions. Lymphocyte adhesion to the continuous endothelial cell lines mHEVa and mHEVc required alpha 4-integrin. Interestingly, lymphocyte alpha 4-integrin bound to VCAM-1 as well as an unknown ligand on the mHEVa cell line. We have demonstrated that this VCAM-1-independent adhesion to the mHEVa cells was not mediated by other known alpha 4-integrin ligands (fibronectin, alpha 4-integrin itself, or MAdCAM-1). Two novel alpha 4-integrin ligands (p50 and p10) were isolated from the mHEVa cell line but not the mHEVc cell line by B cell alpha 4-integrin-specific ligand binding of radiolabeled mHEV cell membrane proteins. These results provide the first direct evidence that novel ligands for alpha 4-integrin exist on membranes from endothelial cells.Key words: B cell, T cell, endothelial cells, integrin, vascular cell adhesion molecule-1, VCAM-1.
Signal transduction mechanisms mediating secretion in goldfish gonadotropes and somatotropes
Authors: Chang John P , Johnson James D , Goor Fredrick Van , Wong Calvin JH , Yunker Warren K , Uretsky Aubrey D , Taylor Daina , Jobin Richard M , Wong Anderson OL , Goldberg Jeffrey I 
Published: April 2011

The intracellular signal transduction mechanisms mediating maturational gonadotropin and somatotropin secretion in goldfish are reviewed. Several major signaling mechanisms, including changes in intracellular [Ca2+], arachidonic acid cascades, protein kinase C, cyclic AMP/protein kinase A, calmodulin, nitric oxide, and Na+/H+antiport, are functional in both cell types. However, their relative importance in mediating basal secretion and neuroendocrine-factor-regulated hormone release differs according to cell type. Similarly, agonist- and cell-type-specificity are also present in the transduction pathways leading to neuroendocrine factor-modulated maturational gonadotropin and somatotropin release. Specificity is present not only in the actions of different regulators within the same cell type and with the same ligand in the two cell types, but this also exists between isoforms of the same neuroendocrine factor within a single cell type. Other evidence suggests that function-selectivity of signaling may also result from differential modulation of Ca2+fluxes from different sources. The interaction of different second messenger systems provide the basis by which regulation of maturational gonadotropin and somatotropin release by multiple neuroendocrine factors can be integrated at the target cell level.Key words: Ca2+signaling, cAMP, PKC, arachidonic acid, NO.